Title of Invention: GAS SUPPLY APPARATUS Abstract: A gas ejector of a gas supply apparatus includes a nozzle portion. The opening of a first-stage restricting cylinder constituting the nozzle portion has a circular cross-sectional shape with a diameter r1. A second-stage restricting cylinder is continuously formed with the first-stage restricting cylinder along a Z direction. The opening of the second-stage restricting cylinder has a circular cross-sectional shape with a diameter r2, and supplies a source gas supplied from the first-stage restricting cylinder to a low-vacuum processing chamber below. At this time, the diameter r2 is set to satisfy “r2>r1”. Detailed Description: TECHNICAL FIELD The present invention relates to a gas supply apparatus for a film formation process. BACKGROUND ART In the field of semiconductor manufacturing, processes such as a film formation process of forming an insulating film or the like on a substrate of an object to be processed such as a wafer, and etching, cleaning, and the like of a film surface formed by film formation are performed. These processes are required to be performed at high speed and with high-quality techniques. For example, together with various high-performance and excellent film formation processes including film formation of a highly insulating thin film, a semiconductor thin film, a high dielectric thin film, a light-emitting thin film, a highly magnetic thin film, a super-hard thin film, and the like, an etching process, peeling, and a cleaning process with high quality have been pursued. Realization of high-quality and uniform film formation on a surface of a wafer (surface of a substrate to be processed) having a large area and high processing speed are highly valued. The various thin-film techniques, and etching, peeling and cleaning processes described above have been applied not only to semiconductor elements but also to various fields of application. In particular, among them, in the thin-film formation technique, a basic technique of promoting nitriding, oxidation and hydrogen bonding by chemical reaction on a surface of a substance such as a metal or an insulator material is important in thin-film formation. Based on this basic technique, a thin film is subjected to various heat treatments and chemical-reaction processes, and thus high-quality thin-film formation is realized. Specifically, in the manufacture of a semiconductor device, there are film formation methods of high-function films such as a low-impedance highly conductive film functioning as circuit wiring in a semiconductor chip, a highly magnetic film having a wiring coil function or a magnet function of a circuit, a high dielectric film having a capacitor function of a circuit, and a highly insulating film having a high insulating function with a little electrical leakage current, the highly insulating film formed by oxidation or nitriding. In order to realize these film formation methods for high-function films, a thermal CVD (Chemical Vapor Deposition) apparatus, a photo-CVD apparatus, a plasma CVD apparatus, a thermal ALD (Atomic Layer Deposition) apparatus, or a plasma ALD apparatus is used. In particular, plasma CVD/ALD apparatuses are often used. For example, the plasma CVD/ALD apparatus is advantageous in that the plasma CVD/ALD apparatus has lower film-formation temperature and can perform a film formation process faster in a shorter time than a thermal/photo CVD/ALD apparatus. For example, in a case where a gate insulating film such as a nitride film (SiON, HfSiON or the like) or an oxide film (SiO2. HfO2) is formed on a wafer which is a substrate to be processed, the following technique using a plasma CVD/ALD apparatus is generally adopted. The thermal CVD/ALD apparatus heats the wafer and the inside of a container to increase reactivity of a supply gas to form a film on the wafer however, if the wafer is exposed to a high temperature, thermal damage or the like leads to a decrease in yield. Therefore, nowadays, film formation with plasma CVD/ALD using plasma is often used in lieu of thermal CVD/ALD. (Plasma) CVD/ALD techniques are disclosed in, for example, Patent Documents 1 to 3. In a conventional film formation processing apparatus using plasma CVD/ALD, thermal CVD/ALD or the like as disclosed in Patent Document 1, a method is adopted in which the film formation apparatus is filled with gas and the filled gas is activated by plasma energy or thermal energy, and a thin film is deposited by a chemical reaction process with the gas supplied to a surface of a wafer. The activated gas filled in the film formation processing apparatus only has a random gas flow velocity due to Brownian motion, and a gas particle itself does not have high speed. Therefore, the method is effective for a deposition film formation reaction on a surface of a substrate, but is not suitable for uniformly forming a film on an extremely uneven surface of a substrate and for uniformly forming a three-dimensional film surface. In addition, in the case of a highly reactive gas, since chemical reaction time is short, the lifetime is very short. Therefore, there is a disadvantage that reaction is promoted only on a surface of a substrate, a supply gas does not reach an extremely uneven surface with high aspect ratio, and uniform film formation cannot be performed. In this case, it is necessary to lead a reactant gas to the inside of a wafer in a short time so that film formation is performed by uniformly carrying out reaction even inside the wafer, or to give energy to gas filled inside the wafer to convert the gas into an activated gas. In a CVD/ALD film formation processing apparatus disclosed in Patent Document 2, gas is uniformly supplied into a container and deposited on entirety of a wafer. However, there is a problem that in a case where reactivity of the gas is high, the gas loses the reactivity before reaching the wafer. Therefore, there are known a method of generating plasma in a container to generate a highly reactive gas and supplying the gas to a substrate, and a method of increasing the temperature inside a container or a wafer to increase reactivity. In a plasma CVD/ALD apparatus using plasma disclosed in Patent Document 3, energy of plasma is given to gas being supplied, and the gas is converted into a highly reactive gas and supplied. In that case, there is an advantage that the temperature inside a wafer or a container can be set lower than the temperature in the case of thermal film formation; however, since a plasma generation source and a surface to be processed are required to be located close to each other, there is a disadvantage that the substrate itself, which is located close to the plasma generation source, is damaged due to an influence of plasma. In addition, when the conventional CVD/ALD film formation processing apparatus and the currently operating plasma CVD/ALD apparatus are compared with each other, the currently operating plasma CVD/ALD apparatus is suitable for a three-dimensional film formation process on a relatively less uneven surface of a wafer. However, it is substantially impossible to realize a three-dimensional film formation process on a more uneven surface of a wafer having higher aspect ratio and to obtain a high-quality three-dimensional film formation structure. In a manufacturing method for manufacturing a three-dimensional-structure semiconductor disclosed in Patent Document 4, it is necessary to form a uniform barrier film located around a TSV (through-silicon via) structure. In this case, there is limitation in uniform film formation in the depth direction. Therefore, the barrier film to be formed is divided into a plurality of layers in the depth direction, and several layers are formed each time. PRIOR ART DOCUMENTS Patent Documents Patent Document 1: Japanese Patent Application Laid-Open No. 2004-111739 Patent Document 2: Japanese Patent Application Laid-Open No. 309.437.6602 Patent Document 3: Japanese Patent Application Laid-Open No. 2001-135628 Patent Document 4: Japanese Patent Application Laid-Open No. 20014-86498 SUMMARY Problem to be Solved by the Invention As described above, in the conventional thin-film formation techniques, since the film formation process is performed by supplying a supply gas and setting the inside of the film formation processing apparatus at a predetermined pressure, it is not necessary to supply gas having directivity at high speed. Therefore, the conventional thin-film formation techniques are not suitable for a film formation process for an uneven surface, which has been recently demanded. The techniques are particularly not suitable for a film formation process for a wafer having high aspect ratio, a representative example of which is a wafer having a deep hole. In addition, a method is suitable for supplying a highly reactive gas to a surface of a wafer in a short time. In the method, a single restricting cylinder (orifice) is provided as means for quickly supplying gas to a low-vacuum processing chamber to increase gas supply speed, the gas is ejected in a low-vacuum environment in the low-vacuum processing chamber, and thus, the gas is ejected at an ultra-high speed exceeding Mach. In that case, it is necessary to set the pressure difference between the pressure in a gas supply apparatus and the pressure in the low-vacuum processing chamber in a low-vacuum state to be greater than or equal to a predetermined pressure ratio. As the pressure difference is greater or the pressure inside the low-vacuum processing chamber is lower, the gas is supplied at higher speed and the gas can be supplied on the surface of the wafer in a shorter time. If the diameter of the opening of a flow path in the restricting cylinder is reduced and the pressure difference is increased, flow velocity becomes faster and thus gas supply time becomes shorter. However, in a case of ejecting gas at an ultra-high speed exceeding Mach, the gas speed affects a gas flow velocity frame (gas jet speed) at the gas impact pressure and the temperature condition of Mach speed, and brings about an effect of extremely lowering the gas flow velocity at a certain ejection position. As a result, a phenomenon called a Mach disk condition (condition where the gas flow velocity is extremely lowered at a certain ejection position) occurs. It is preferable to minimize the phenomenon of this Mach disk condition; however, no specific solution has been found. The present invention solves the above-described problems. An object of the present invention is to provide a gas supply apparatus capable of effectively suppressing a phenomenon in which extreme deceleration of gas occurs in association with an impact pressure and a temperature condition generated by a gas supplied to a substrate at an ultra-high speed exceeding Mach when the gas is supplied to the substrate at the ultra-high speed. Means to Solve the Problem A gas supply apparatus according to the present invention includes: a mounting portion for mounting a substrate to be processed; and a gas ejector which is provided above the mounting portion and supplies gas from a processing chamber having an opening on a bottom surface to the substrate to be processed. The gas ejector includes: a primary accommodating chamber which temporarily accommodates gas supplied from a gas supply port; the processing chamber; and a nozzle portion which is provided between the primary accommodating chamber and the processing chamber. The nozzle portion has: a first restricting cylinder whose opening has a circular cross-sectional shape with a first diameter in plan view, and which supplies the gas in the primary accommodating chamber downward; and a second restricting cylinder whose opening has a circular cross-sectional shape with a second diameter in plan view, and which supplies the gas supplied from the first restricting cylinder to the processing chamber. The first diameter is set such that pressure difference between the primary accommodating chamber and the processing chamber is greater than or equal to a predetermined pressure ratio. The second diameter is set to be longer than the first diameter. Effects of the Invention In the gas ejector of the gas supply apparatus of the present invention according to claim 1, the first restricting cylinder having the first diameter in the nozzle portion can give directivity to gas to be ejected to the processing chamber. Thus, gas can be supplied to the substrate to be processed at an ultra-high speed exceeding Mach. In this case, due to existence of the second restricting cylinder provided between the first restricting cylinder and the processing chamber, it is possible to suppress a Mach disk phenomenon in which ejected gas is extremely decelerated by the impact pressure and the temperature condition generated by the gas ejecting at an ultra-high speed. As a result, the gas supply apparatus of the present invention according to claim 1 has the effect of being able to supply gas suitable for film formation on a surface of a wafer with high aspect ratio to a substrate to be processed. The objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 1 of the present invention. FIG. 2 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 2 of the present invention. FIG. 3 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 3 of the present invention. FIG. 4 is an explanatory view (part 1) illustrating a configuration of a gas supply apparatus according to Embodiment 4 of the present invention. FIG. 5 is an explanatory view (part 2) illustrating the configuration of the gas supply apparatus according to Embodiment 4 of the present invention. FIG. 6 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 5 of the present invention. FIG. 7 is an explanatory view schematically illustrating a speed condition of a gas jet using the gas supply apparatus according to Embodiment 1. FIG. 8 is an explanatory view schematically illustrating a pressure condition of a gas jet using the gas supply apparatus according to Embodiment 1. FIG. 9 is an explanatory view schematically illustrating a speed condition of a gas jet using a conventional gas supply apparatus. FIG. 10 is an explanatory view schematically illustrating a pressure condition of the gas jet using the conventional gas supply apparatus. FIG. 11 is an explanatory view schematically illustrating a speed condition of a gas jet in a case where the pressure ratio of a primary accommodating chamber to a low-vacuum processing chamber is less than 30 times. FIG. 12 is an explanatory view schematically illustrating a pressure condition of the gas jet in a case where the pressure ratio of the primary accommodating chamber to the low-vacuum processing chamber is less than 30 times. FIG. 13 is an explanatory view schematically illustrating a Mach disk generation structure in the case of using the conventional gas supply apparatus. FIG. 14 is an explanatory view schematically illustrating effects in the case of using the gas supply apparatus according to the present embodiment. DESCRIPTION OF EMBODIMENTS Embodiment 1 FIG. 1 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 1 of the present invention. In FIG. 1, an XYZ orthogonal coordinate system is illustrated. As illustrated in FIG. 1, the gas supply apparatus according to Embodiment 1 includes: a mounting table 19 (mounting portion) for mounting a wafer 25 which is a substrate to be processed; and a gas ejector 1 which is provided above the mounting table and supplies gas from a low-vacuum processing chamber 18 (processing chamber) having an opening on a bottom surface to the wafer 25 below. The gas ejector 1 has, as main components, a primary accommodating chamber 11, a gas supply port 12, a first-stage restricting cylinder 13 (first restricting cylinder), a second-stage restricting cylinder 14 (second restricting cylinder), and the low-vacuum processing chamber 18 (processing chamber). A nozzle portion 10 is formed of a configuration including a group of the restricting cylinders 13 and 14. That is, the nozzle portion 10 is provided between the primary accommodating chamber 11 and the low-vacuum processing chamber 18. The opening of the first-stage restricting cylinder 13 constituting the nozzle portion 10 has a circular cross-sectional shape with a diameter r1 (first diameter) on XY plane (in plan view). The first-stage restricting cylinder 13 supplies a source gas G1 in the primary accommodating chamber 11 downward (in a −Z direction). The diameter r1 is set such that pressure difference between the primary accommodating chamber 11 and the low-vacuum processing chamber 18 is greater than or equal to a predetermined pressure ratio. The second-stage restricting cylinder 14 is continuously formed with the first-stage restricting cylinder 13 along a Z direction. The opening of the bottom surface of the second-stage restricting cylinder 14 has a circular cross-sectional shape with a diameter r2 (second diameter) on XY plane (in plan view). The second-stage restricting cylinder 14 supplies the source gas G1 supplied from the first-stage restricting cylinder 13 to the low-vacuum processing chamber 18 below. The diameter r2 is set so as to satisfy “r2>r1”. For example, the diameter r1 of the first-stage restricting cylinder 13 is 1.35 mm in diameter, the depth (formation length extending in the Z direction) of the first-stage restricting cylinder 13 is 1 mm, the diameter r2 of the second-stage restricting cylinder 14 is 8 mm in diameter, and the depth (formation length extending in the Z direction) of the second-stage restricting cylinder 14 is 4 mm. For example, nitrogen gas is supplied as the source gas G1 at a flow rate of 4 slm (standard liter per minute). Therefore, the source gas G1 that has passed through the first-stage restricting cylinder 13 becomes an ultra-high-speed gas and is supplied into the low-vacuum processing chamber via the second-stage restricting cylinder 14. The primary accommodating chamber 11 temporarily accommodates the source gas G1 supplied from the gas supply port 12. The pressure in the primary accommodating chamber 11 is a primary pressure. After the source gas G1 supplied from the gas supply port 12 passes through the primary accommodating chamber 11, a secondary pressure is determined by the first-stage restricting cylinder 13. The source gas G1 is supplied into the low-vacuum processing chamber 18 via the second-stage restricting cylinder 14. At that time, a pressure ratio PC between the primary pressure in the primary accommodating chamber 11 and the secondary pressure in the low-vacuum processing chamber 18 is set to greater than or equal to 30 times. Then, the flow velocity of the source gas G1 that has passed through the first-stage restricting cylinder 13 becomes a flow velocity greater than or equal to Mach due to the pressure ratio PC. Due to the existence of the second-stage restricting cylinder 14, a phenomenon in which a Mach disk condition generated by a high-speed jet of the source gas G1 occurs is suppressed. Then, the source gas G1 is supplied into the low-vacuum processing chamber 18. For example, if the primary pressure in the primary accommodating chamber 11 is 30 kPa and the pressure in the low-vacuum processing chamber 18 is 266 Pa, the maximum Mach number of the source gas G1 as the ultra-high-speed gas exceeds “5” and is supplied to the wafer 25 on the mounting table 19. At this time, since the Mach disk condition which is likely to occur is effectively suppressed by the existence of the second-stage restricting cylinder 14, the gas supply apparatus can supply the gas to the wafer at a higher speed than a conventional gas supply apparatus. That is, due to provision of the second-stage restricting cylinder 14, pressure distribution and flow-velocity distribution in the low-vacuum processing chamber 18 can be relaxed to avoid an occurrence of a Mach disk MD condition, and the source gas G1 is supplied into the low-vacuum processing chamber 18 and is supplied to the wafer 25 placed on the mounting table 19 (wafer table). After the gas has been reacted, the gas is exhausted from an exhaust port 21 provided between the gas ejector 1 and the mounting table 19. (Comparison with Conventional Configuration and the Like) FIG. 7 is an explanatory view schematically illustrating a speed condition of a gas jet using the gas supply apparatus according to Embodiment 1 having the nozzle portion 10. FIG. 8 is an explanatory view schematically illustrating a pressure condition of the gas jet using the gas supply apparatus according to Embodiment 1 having the nozzle portion 10. FIG. 9 is an explanatory view schematically illustrating a speed condition of a gas jet using a conventional gas supply apparatus having a nozzle portion configured only of a first-stage restricting cylinder 13. FIG. 10 is an explanatory view schematically illustrating a pressure condition of the gas jet using the conventional gas supply apparatus having the nozzle portion configured only of the first-stage restricting cylinder 13. In FIGS. 7 to 10, the uppermost hatched portion corresponds to, for example, a formation region of an upper electrode 22 in Embodiment 4 to be described later. In FIGS. 11 and 12, the uppermost hatched portion corresponds to the formation region of the upper electrode 22 in Embodiment 4 to be described later. As illustrated in FIGS. 8 and 10, the above-described pressure ratio PC of the primary pressure to the secondary pressure is set to greater than or equal to 30 times. As is apparent from the comparison between FIG. 7 and FIG. 9, by avoiding the phenomenon in which a Mach disk MD occurs, the gas supply apparatus according to Embodiment 1 can supply the source gas G1 to the wafer 25 without extremely lowering the speed of the source gas G1. In contrast, as illustrated in FIG. 9, a Mach disk MD is generated in the conventional gas supply apparatus. FIG. 11 is an explanatory view schematically illustrating a speed condition of a gas jet in a case where the pressure ratio PC of the primary accommodating chamber 1 to the low-vacuum processing chamber 18 is less than 30 times in the configuration according to Embodiment 1. FIG. 12 is an explanatory view schematically illustrating a pressure condition of the gas jet in the case where the pressure ratio PC of the primary accommodating chamber 11 to the low-vacuum processing chamber 18 is less than 30 times in the configuration in Embodiment 1. In FIGS. 11 and 12, the uppermost hatched portion corresponds to the formation region of the upper electrode 22 in Embodiment 4 to be described later. As illustrated in FIG. 12, the above-described pressure ratio PC of the primary pressure to the secondary pressure is set to less than 30 times. As is apparent from the comparison between FIG. 7 and FIG. 11, in a case where the pressure ratio PC is greater than or equal to 30 times, speed distribution with a higher jet velocity than that in a case where the pressure ratio PC is less than 30 times is obtained, and gas having directivity can be reliably supplied to the surface of the wafer 25. (Effects Provided by Second-Stage Restricting Cylinder 14) FIG. 13 is an explanatory view schematically illustrating a Mach disk generation structure in a case of using the conventional gas supply apparatus having the nozzle portion configured only of the first-stage restricting cylinder 13. In a case where when the source gas G1 which is the supply gas passes through the first-stage restricting cylinder 13 (orifice), the primary pressure of the primary accommodating chamber 11 is higher than the secondary pressure of the low-vacuum processing chamber 18, that is, ejection pressure of the source gas G1 from the first-stage restricting cylinder 13 is higher than the pressure in the low-vacuum processing chamber 18, a flow having passed through an outlet (orifice outlet) of the first-stage restricting cylinder 13 causes a phenomenon called a shock cell structure (shock cell), and the above shock cell structures are periodically observed in a downstream direction. The shock cell structure means a structure of a shock wave in which reflected shock waves RS to be described later are repeatedly obtained at boundary regions JB (Jet Boundary) to be described below. Such a case where the pressure at the orifice outlet is greater than the pressure inside the low-vacuum processing chamber 18 is called under expansion and the flow expands after passing through the orifice outlet. In a case where the pressure at the orifice outlet is further greater than the pressure in the low-vacuum processing chamber 18, the gas has not yet fully expanded. Therefore, expansion waves EW are generated at an edge of the orifice outlet, and the gas greatly expands to the outside. In a case where the Mach number of the gas is great, the expansion waves EW are reflected by the boundary region JB (Jet Boundary), become compression waves and return to a jet center axis side. Note that the compression wave is a wave whose pressure is higher than a reference value. When the compression wave passes through, the pressure at the point where the compression wave passes rises. The expansion wave means a wave whose pressure is lower than a reference value. When the expansion wave passes through, the pressure at the point where the expansion wave passes lowers. As described, in a case where the pressure difference before and after the gas passes through the nozzle portion is great, the formed compression waves catch up with preceding compression waves to form barrel-shaped barrel shock waves BS (barrel shock). When the pressure difference becomes further greater, the barrel shock waves BS cannot normally intersect on the center axis of the jet, and in the axisymmetric jet, a disk-shaped normal shock wave called a Mach disk MD (Mach shock wave) is formed. The flow behind the Mach disk MD is a subsonic flow. A reflected shock wave RS (Reflection Shock) is generated from an end of the barrel shock wave BS. Note that a triple point TP is a point at which the barrel shock wave BS which is a compression wave, the Mach disk MD, and the reflected shock wave RS intersect. In contrast, as illustrated in FIG. 14, in the gas ejector 1 according to Embodiment 1, since the second-stage restricting cylinder 14 continuously formed with the first-stage restricting cylinder 13 is provided, expanded waves EW are reflected by a side surface of the second-stage restricting cylinder 14, and therefore barrel shock waves BS can normally intersect on a center axis XC of the jet. Therefore, occurrence of a Mach disk MD can be avoided. (Effects of the Invention and the Like) In the gas ejector 1 of the gas supply apparatus according to Embodiment 1, the first-stage restricting cylinder 13 provided in the nozzle portion 10 and having the opening with the diameter r1 can give directivity to the source gas G1 to be ejected to the low-vacuum processing chamber 18. Thus, the gas can be supplied to the wafer 25 which is the substrate to be processed at an ultra-high speed exceeding Mach. In this case, due to existence of the second-stage restricting cylinder 14 provided between the first-stage restricting cylinder 13 and the low-vacuum processing chamber 18, it is possible to effectively suppress an occurrence of a Mach disk MD in which the ejected source gas G1 is extremely decelerated due to impact pressure and temperature caused by the source gas G1 ejecting at an ultra-high speed. As a result, the gas supply apparatus according to Embodiment 1 has effects of being able to supply the source gas G1 suitable for formation of a film having a three-dimensional structure obtained by forming a film on a surface of the wafer 25 with high aspect ratio. For example, a reactive gas is supplied as the source gas G1 to the wafer 25. Furthermore, the gas supply apparatus according to Embodiment 1 can supply the source gas G1 in a high-speed state to the wafer 25 which is a substrate to be processed, by setting the pressure ratio PC of the primary pressure in the primary accommodating chamber 11 to the secondary pressure in the low-vacuum processing chamber 18 to greater than or equal to 30 times. In addition, the gas supply apparatus according to Embodiment 1 can more effectively suppress a Mach disk MD, by setting the diameter r2 of the second-stage restricting cylinder 14 to be within 30 mm in diameter. In addition, it is preferable to adopt a first aspect where in the gas supply port 12, the primary accommodating chamber 11, the first-stage restricting cylinder 13, and the second-stage restricting cylinder 14 constituting the gas ejector 1, a gas contact region, which is a region to be brought into contact with the source gas G1, is formed to include quartz or an alumina material as a constituent material. A reactive gas is generally used as the source gas G1. Therefore, in the gas ejector 1 according to Embodiment 1 adopting the first aspect, at least the above gas contact region is formed of quartz or an alumina material. Since a quartz material surface and an alumina surface are chemically stable to the above-described reactive gas, it is possible to supply the reactive gas into the low-vacuum processing chamber 18 in a state where there is little chemical reaction between the reactive gas and the gas contact region in contact with the reactive gas. Furthermore, it is possible to reduce generation of corrosive substances as by-products accompanying chemical reaction with the reactive gas in the gas ejector 1. As a result, it is possible to supply, as the source gas G1, a clean reactive gas into the low-vacuum processing chamber 18, the reactive gas to be supplied containing no contaminants. Therefore, there is an effect of improving film-formation quality of the film formed on the wafer 25. Furthermore, it is preferable to adopt a second aspect where the gas ejector 1 is heated to 100° C. or higher when the source gas G1 is supplied to the wafer 25, and the heated source gas G1 is supplied to the wafer 25. Note that a configuration such as providing a heating processing mechanism such as a hot plate or the like near the gas ejector 1 is considered in order to perform heating processing. In the gas supply apparatus adopting the second aspect, the reactive gas used as the source gas G1 is subjected to heating processing and receives thermal energy. Therefore, the gas supply apparatus adopting the second aspect can supply a more highly reactive gas to the low-vacuum processing chamber 18, has an effect of forming a film on the wafer 25 at a higher speed, and has an effect of being able to perform a high-speed film formation process. In addition, it is preferable to adopt a third aspect where the source gas G1 supplied from the gas supply port 12 is a gas containing at least nitrogen, oxygen, fluorine, and hydrogen. In the gas supply apparatus adopting the third aspect, the source gas G1 supplied from the gas supply port 12 is a gas containing at least nitrogen, oxygen, fluorine, and hydrogen gas. Therefore, the gas supply apparatus adopting the third aspect can be used not only for formation of an insulating film such as a nitride film or an oxide film, but also for resist peeling and surface treatment of the wafer 25 with high aspect ratio using an activated gas of a fluorinated gas serving as an etching gas or a cleaning gas. Furthermore, by applying an ultra-high-speed gas such as a hydrogen radical gas to the surface of the wafer 25, the source gas G1 usable for applications other than insulating film formation, an etching process, and a cleaning function can also be supplied. Therefore, the gas supply apparatus can be used for various film formation processes. In lieu of the third aspect, a fourth aspect where the source gas G1 supplied from the gas supply port 12 is a precursor gas may be adopted. By using the precursor gas as the source gas G1 supplied from the gas supply port 12, the source gas G1 can be used as a reactive gas for surface treatment of the wafer with high aspect ratio. In addition, the precursor gas to be a material of a deposited metal in film formation, the precursor gas necessary for film formation on the surface of the wafer 25, can be also supplied to the surface of the wafer 25 to perform film formation. It is preferable to adopt as a fifth aspect a configuration in which a flow rate control unit that controls the gas flow rate of the source gas G1 supplied from the gas supply port 12 is provided such that the pressure is set to a pressure lower than or equal to the atmospheric pressure (1013.25 hPa) in the low-vacuum processing chamber 18 and higher than or equal to 10 kPa. Note that for example, a configuration in which a gas flow rate control device (mass flow controller; MFC) is provided in a supply path between a supply unit of the source gas G1 and the gas supply port 12 of the source gas G1, and the gas flow rate control device is controlled is considered as the flow rate control unit. The gas supply apparatus adopting the fifth aspect can improve stability of the flow velocity of the ultra-high-speed gas in the source gas G1 ejected from the nozzle portion 10 of the gas ejector 1 into the low-vacuum processing chamber 18, and can exhibit the effect of improving film forming quality, such as uniformization of the thickness or the like of the film formed on the surface of the wafer 25. Embodiment 2 FIG. 2 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 2 of the present invention. In FIG. 2, an XYZ orthogonal coordinate system is illustrated. As illustrated in FIG. 2, the gas supply apparatus according to Embodiment 2 includes: a mounting table 19 (mounting portion) for mounting a wafer 25 which is a substrate to be processed; and a gas ejector 2 which is provided above the mounting table 19 and supplies gas from a low-vacuum processing chamber 18 having an opening to the wafer 25. The gas ejector 2 includes a primary accommodating chamber 11, a gas supply port 12, a first-stage restricting cylinder 13 (first restricting cylinder), a second-stage restricting cylinder 14 (second restricting cylinder), a third-stage restricting cylinder 15 (third restricting cylinder), and the low-vacuum processing chamber 18 as main components. A nozzle portion 20 is formed of a configuration including a group of the restricting cylinders 13 to 15. That is, the nozzle portion 20 is provided between the primary accommodating chamber 11 and the low-vacuum processing chamber 18. Similarly to Embodiment 1, the opening of the first-stage restricting cylinder 13 constituting the nozzle portion 20 has a circular cross-sectional shape with a diameter r1 in plan view, and supplies a source gas G1 in the primary accommodating chamber 11 downward. The second-stage restricting cylinder 14 is continuously formed with the first-stage restricting cylinder 13 along a Z direction. Similarly to Embodiment 1, the opening of the bottom surface of the second-stage restricting cylinder 14 has a circular cross-sectional shape with a diameter r2 in plan view, and supplies the source gas G1 supplied from the first-stage restricting cylinder 13 downward. The third-stage restricting cylinder 15 is continuously formed with the second-stage restricting cylinder 14 along the Z direction. The opening of the bottom surface of the third-stage restricting cylinder 15 has a circular cross-sectional shape with a diameter r3 (third diameter) on XY plane (in plan view). The third-stage restricting cylinder 15 supplies the source gas G1 supplied from the second-stage restricting cylinder 14 to the low-vacuum processing chamber 18 below. The diameter r3 is set so as to satisfy “r3>r2”. For example, in a case where the diameter r1 of the first-stage restricting cylinder 13 is 1.35 mm in diameter, the depth of the first-stage restricting cylinder 13 is 1 mm, the diameter r2 of the second-stage restricting cylinder 14 is 8 mm and the depth of the second-stage restricting cylinder 14 is 4 mm, the diameter r3 of the third-stage restricting cylinder 15 is set to 20 mm in diameter, the depth (formation length extending in the Z direction) of the third-stage restricting cylinder 15 is set to 46 mm, and a nitrogen gas, for example, is supplied at a flow rate of 4 slm. Then, the source gas G1 passed through the first-stage restricting cylinder 13 becomes an ultra-high-speed gas and is supplied into the low-vacuum processing chamber 18 via the second-stage restricting cylinder 14 and the third-stage restricting cylinder 15. Note that since the other configurations of the gas ejector 2 are identical to those of the gas ejector 1 according to Embodiment 1, identical reference signs are appropriately given, and the description thereof will be omitted. In the gas ejector 1 of the gas supply apparatus according to Embodiment 2, the nozzle portion 20 is configured of the first-stage restricting cylinder 13, the second-stage restricting cylinder 14, and the third-stage restricting cylinder 15 having the openings with the diameter r1, the diameter r2, and the diameter r3, respectively. Therefore, it is possible to give directivity to the source gas G1 ejected into the low-vacuum processing chamber 18. In this case, similarly to Embodiment 1, existence of the second-stage restricting cylinder 14 can effectively suppress a Mach disk MD phenomenon. In addition, the gas supply apparatus according to the Embodiment 2 has effects similar to those of the gas supply apparatus according to Embodiment 1, and also has the effects in the case of adopting the first to fifth aspects. Furthermore, the gas ejector 2 according to Embodiment 2 further includes the third-stage restricting cylinder 15 as the nozzle portion 20, and the diameter r3 of the third-stage restricting cylinder 15 is set to be longer than the diameter r2 of the second-stage restricting cylinder 14. Therefore, it is possible to supply the source gas G1 to the wafer 25 in a state where the occurrence of Mach disk MD caused by the high-speed jet generated at the pressure ratio PC is suppressed more than in the case of Embodiment 1. Embodiment 3 FIG. 3 is an explanatory view illustrating a configuration of a gas supply apparatus according to Embodiment 3 of the present invention. In FIG. 3, an XYZ orthogonal coordinate system is illustrated. As illustrated in FIG. 3, the gas supply apparatus according to Embodiment 3 includes: a mounting table 19 (mounting portion) for mounting a wafer 25 which is a substrate to be processed; and a gas ejector 3 which is provided above the mounting table and supplies gas from a low-vacuum processing chamber 18 having an opening to the wafer 25. The gas ejector 3 includes a primary accommodating chamber 11, a gas supply port 12, a first-stage restricting cylinder 13 (first restricting cylinder), a hemispherical restricting cylinder 17 (second restricting cylinder), and the low-vacuum processing chamber 18 as main components. A nozzle portion 30 is formed of a configuration including a group of the two restricting cylinders 13 and 17. That is, the nozzle portion 30 is provided between the primary accommodating chamber 11 and the low-vacuum processing chamber 18. Similarly to Embodiment 1, the opening of the first-stage restricting cylinder 13 (first restricting cylinder) constituting the nozzle portion 30 has a circular cross-sectional shape with a diameter r1, and supplies a source gas G1 in the primary accommodating chamber 11 downward. The hemispherical restricting cylinder 17 is continuously formed with the first-stage restricting cylinder 13 along a Z direction. The opening of the bottom surface of the hemispherical restricting cylinder 17 has a circular cross-sectional shape with a diameter r2b (second diameter) on XY plane. The hemispherical restricting cylinder 17 supplies the source gas G1 supplied from the first-stage restricting cylinder 13 to the low-vacuum processing chamber 18 below. The diameter r2b of the bottom surface is set so as to satisfy “r2b>r1”. Since the hemispherical restricting cylinder 17 is formed in a hemispherical shape having an opening at the top, the diameter r2 of the opening is set so as to increase as it goes downward (−Z direction). That is, the diameter r2 of the opening of the hemispherical restricting cylinder 17 in plan view is set to become longer as it goes downward from a diameter r2t (=diameter r1) of the top to a diameter r2b of the bottom surface. Note that since the other configurations of the gas ejector 3 are identical to those of the gas ejector 1 according to Embodiment 1, identical reference signs are appropriately given, and the description thereof will be omitted. In the gas ejector 1 of the gas supply apparatus according to Embodiment 3, the nozzle portion 30 is configured of the first-stage restricting cylinder 13 and the hemispherical restricting cylinder 17 having the openings with the diameter r1 and the diameters r2 (r2t to r2b), respectively. Therefore, it is possible to give directivity to the source gas G1 ejected into the low-vacuum processing chamber 18. In this case, similarly to Embodiment 1, existence of the hemispherical restricting cylinder 17 has the effect of suppressing a Mach disk MD phenomenon. In addition, the gas supply apparatus according to the Embodiment 3 has effects similar to those of the gas supply apparatus according to Embodiment 1, and also has the effects in the case of adopting the first to fifth aspects. Furthermore, the hemispherical restricting cylinder 17 (second restricting cylinder) in the gas ejector 3 according to Embodiment 3 is formed into a hemispherical shape such that the diameter r2 of the opening becomes longer as it approaches the low-vacuum processing chamber 18 (in the −Z direction). Therefore, it is possible to supply the source gas G1 to the wafer 25 in a state where the occurrence of Mach disk MD caused by the high-speed jet generated at the pressure ratio PC is suppressed more than in the case of Embodiment 1. Note that in the above-described configuration of Embodiment 3, as a modification, a third-stage restricting cylinder may be further provided under the hemispherical restricting cylinder 17, similarly to the third-stage restricting cylinder 15 according to Embodiment 2. As the shape of the third-stage restricting cylinder according to Embodiment 3, a columnar shape having a diameter identical to the diameter r2b of the bottom surface of the hemispherical restricting cylinder 17 or the like is considered. Embodiment 4 FIGS. 4 and 5 are explanatory views illustrating a configuration of a gas supply apparatus according to Embodiment 4 of the present invention. FIG. 4 is a cross-sectional view, and FIG. 5 is a perspective view. In each of FIGS. 4 and 5, an XYZ orthogonal coordinate system is illustrated. As illustrated in FIGS. 4 and 5, the gas supply apparatus according to Embodiment 4 includes a mounting table 19 (mounting portion) for mounting a wafer 25 which is a substrate to be processed; and a gas ejector 4 which is provided above the mounting table 19 and supplies gas from a low-vacuum processing chamber 18 having an opening to the wafer 25. The gas ejector 4 has a primary accommodating chamber 11, a gas supply port 12, a first-stage restricting cylinder 13X (first restricting cylinder), a second-stage restricting cylinder 14X (second restricting cylinder), an upper electrode 22, a lower electrode 24, and the low-vacuum processing chamber 18 as main components. A nozzle portion 40 is formed of a configuration including a group of the two restricting cylinders 13X and 14X, and the lower electrode 24. That is, the nozzle portion 40 is provided between the primary accommodating chamber 11 and the low-vacuum processing chamber 18. The upper electrode 22 and the lower electrode 24 each having a dielectric such as alumina on surfaces facing each other are circular on XY plane (in plan view) and are provided so as to face each other. Note that a configuration may be possible in which a dielectric is provided only on one of the surfaces of the upper electrode 22 and the lower electrode 24, the surfaces facing each other. That is, the gas ejector 4 has the upper electrode 22 and the lower electrode 24 (first and second electrodes) provided so as to face each other. A discharge space is formed between the upper electrode 22 and the lower electrode 24. At least one of the upper electrode 22 and the lower electrode 24 has a dielectric on the surface forming the discharge space. Specifically, the upper electrode 22 is disposed near the bottom surface in the primary accommodating chamber 11. In contrast, the lower electrode 24 is arranged under the bottom surface of the primary accommodating chamber 11i so as to form part of the bottom surface of the primary accommodating chamber 1. A through hole provided at the center of the lower electrode 24 serves as the first-stage restricting cylinder 13X. Similarly to the first-stage restricting cylinder 13 according to Embodiment 1, the opening of the first-stage restricting cylinder 13X (first restricting cylinder) constituting the nozzle portion 40 has a circular cross-sectional shape with a diameter r1 (first diameter) on XY plane (in plan view), and supplies a source gas G1 in the primary accommodating chamber 11 downward. The second-stage restricting cylinder 14X is continuously formed just under the lower electrode 24 including the first-stage restricting cylinder 13X along a Z direction. Similarly to the second-stage restricting cylinder 14 according to Embodiment 1, the opening of the second-stage restricting cylinder 14X has a circular cross-sectional shape with a diameter r2 (second diameter) on XY plane (in plan view), and supplies the source gas G1 supplied from the first-stage restricting cylinder 13 to the low-vacuum processing chamber 18 below. The diameter r2 is set so as to satisfy “r2>r1”. As described above, the gas ejector 4 according to Embodiment 4 has a gas ionization unit inside. The gas ionization unit ionizes the source gas G1 to obtain an ionized or radicalized gas in the discharge space between the upper electrode 22 and the lower electrode 24 facing each other with the dielectric interposed therebetween. The gas ionization unit has a discharge space between the upper electrode 22 and the lower electrode 24 facing each other with the dielectric interposed therebetween. The gas ionization unit can apply an alternating voltage between the upper electrode 22 and the lower electrode 24, generate dielectric-barrier discharge in the discharge space, and supply an ionized gas or a radicalized gas obtained by ionizing or radicalizing the source gas G1 into the low-vacuum processing chamber 18 via the second-stage restricting cylinder 14X. As described above, the gas ejector 4 according to Embodiment 4 is characterized by including the gas ionization unit which is provided near a boundary region between the primary accommodating chamber 11 and the nozzle portion 40, and produces an ionized gas or a radicalized gas which is an ionized or radicalized source gas obtained by ionizing the source gas G1 supplied from the gas supply port 12. Note that since the other configurations of the gas ejector 4 are identical to those of the gas ejector 1 according to Embodiment 1, identical reference signs are appropriately given, and the description thereof will be omitted. In the gas ejector 1 of the gas supply apparatus according to Embodiment 4, the nozzle portion 40 is configured of the first-stage restricting cylinder 13X and the second-stage restricting cylinder 14X having the openings with the diameter r1 and the diameter r2, respectively. Therefore, it is possible to give directivity to the source gas G1 ejected into the low-vacuum processing chamber 18. In this case, similarly to Embodiment 1, existence of the second-stage restricting cylinder 14X has the effect of capable of suppressing a Mach disk MD phenomenon. In addition, the gas supply apparatus according to the Embodiment 4 has effects similar to those of the gas supply apparatus according to Embodiment 1, and also has the effects in the case of adopting the first to fifth aspects. In this case, as heating processing according to the second aspect of Embodiment 4, a discharge process between the upper electrode 22 and the lower electrode 24 can be utilized. Furthermore, the gas ejector 4 according to Embodiment 4 can cause the above gas ionization unit to perform gas discharge in the gas ejector 4, and can directly apply an ionized gas or a radicalized gas which is a directional ultra-high-speed jet gas to the surface of the wafer 25 from the low-vacuum processing chamber 18. Therefore, as compared with the plasma CVD/ALD apparatus which is a conventional film forming apparatus, the gas ejector 4 according to Embodiment 4 can apply an activated ionized gas or an activated radicalized gas having higher density and a higher electric field to the surface of the wafer 25, and realize a higher-quality film formation process. The gas ejector 4 has effects of easily forming a film on the wafer 25 with high
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