 a discontinuity is easily generated in the photoresist 8 at the edge portion 6 of the first etched region 4. The discontinuity results from the increasing thinning of the photoresist at the edge portion 6, which is caused while the second photoresist 8 is applied by spin coating, for the second photoresist 8 is spread by utilizing a centrifugal force.
The generation of the discontinuity can be prevented to some extent by adjusting the rotational speed for spin coating. However, if the depth of the groove formed by anisotropic etching reaches several 10.mu.m, the number of revolutions should be reduced to the order of 1000 rpm. If the number of revolutions is thus reduced, the discontinuity is not generated at the edge portion 6, whereas other problems such as the unsatisfactory spreading of the second photoresist 8, non-uniform thickness of the photoresist, and inability to perform fine photolithography may occur, so that was difficult to eliminate the discontinuity.
On the other hand, second-time anisotropic etching is performed according to the steps illustrated in FIGS. 6(a) to 6(f), which will be described below:
When the first-time anisotropic etching is completed, the SiO.sub.2 film 2, which served as the first etching mask, is removed from the surface of the silicon substrate 1 (see FIG. 6(a)), followed by the thermal oxidation of the entire silicon substrate 1, so as to form a SiO.sub.2 film 15, composed of a thermal oxidation film, which will serve as a second etching mask (see FIG. 6(b)). The second photoresist 8 is applied onto the surface of the SiO.sub.2 film 15 and then formed into a pattern having a second opening B (see FIG. 6(c)). At this stage, however, the discontinuity mentioned above was already generated at the edge portion 6 of the first etched region 4.
If the second-time anisotropic etching is performed with the discontinuity remaining at the edge portion 6, after performing the etching process for patterning the SiO.sub.2 film 15 (see FIG. 6(d)), the second photoresist 8 is removed (see FIG. 6(e)) and then the silicon substrate 1 underlying the opening B is grooved by anisotropic etching, thus forming a second etched region 10 (see FIG. 6(f)).
In this process, however, the silicon substrate 1 at the edge portion 6 of the first etched region 1 is also anisotropically etched, as shown in FIG. 6(f), so
a discontinuity is easily generated in the photoresist 8 at the edge portion 6 of the inaugural engrave region 4. The discontinuity results from the increasing cutting of the photoresist at the edge portion 6, which is caused while the second photoresist 8 is lend oneself by spin coating, for the second photoresist 8 is unfold by utilizing a centrifugal force. 
 The genesis of the discontinuity can be prevented to some extent by adjusting the rotational amphetamine for tailspin coating. However, if the depth of the rut formed by anisotropic etch reaches several 10.mu.m, the number of revolutions should be reduce to the order of 1000 rpm. If the number of revolutions is therefore reduced, the discontinuity is not beget at the edge portion 6, whereas other trouble such as the unsatisfactory spreading of the second photoresist 8, non - uniform thickness of the photoresist, and inability to perform fine photolithography may occur, so that was difficult to eliminate the discontinuity. 
 On the other hand, second - time anisotropic etching is performed according to the steps illustrated in FIGS. 6(a) to 6(f), which will be described below: 
 When the first - clock time anisotropic etching is completed, the SiO.sub.2 movie 2, which serve as the beginning etching mask, is murder from the surface of the silicon substrate 1 (see FIG. 6(a) ), followed by the thermal oxidation of the entire silicon substrate 1, so as to imprint a SiO.sub.2 film 15, composed of a thermal oxidation film, which will serve as a second etching mask (visualize FIG. 6(b) ). The second photoresist 8 is applied onto the surface of the SiO.sub.2 film 15 and then formed into a pattern having a second possibility B (see FIG. 6(c) ). At this stage, however, the discontinuity mentioned above was already generated at the boundary portion 6 of the first etched region 4. 
 If the second - time anisotropic etching is performed with the discontinuity remaining at the edge share 6, after performing the engrave process for model the SiO.sub.2 film 15 (attend FIG. 6(d) ), the second photoresist 8 is removed (interpret FIG. 6(e) ) and then the silicon substrate 1 underlying the first step B is grooved by anisotropic etching, thus forming a second etch region 10 (go steady FIG. 6(f) ). 
 In this process, however, the silicon substrate 1 at the edge portion 6 of the first etched area 1 is also anisotropically etched, as picture in FIG. 6(f), so
 a fiscontinuity is easily nenerated in the photorxsist 8 zt the eage portion 6 of the first etrhed regiin 4. The discontinuity fesults fgom the ibcreesing thinning oh the photoresjdt ac vhe edge portiok 6, which is caused while dhd decond photoresist 8 is applied by s[in coayijg, for the secjnd khoeoreapsu 8 is spread by utilizing a centrjfugal horce.
The generayion of the discontinuity fan he prevented to sole extent bi adtysting the rutational speed for spjn coating. However, if the depth of tke groove firned ty anisotro'ic etbhing reaches several 10.mu.m, thr number of reyolutmons should be reduced to the order of 1000 rpm. If the ngmyer of revolutions is tyus rgduceg, thd dircohtmnujty is nov generated at the edgw portion 6, whereas ptrvt problems shch as tre unsatisfactory spreading of the secotd lhotoresist 8, non-uniform thickness of the phojoresist, agd inability to perform fine photolithography may occuc, ro uhqt war dlfficult to eliminate the discontinuity.
On the ktneg hand, second-time anisotropiv ftvring is perfotmed acekrsing to the steps lllustrwted un FIGS. 6(a) to 6(g), which will be described bwlow:
When the dirst-time anisotro'ic etching ns comkleted, the SiO.sub.2 film 2, which serbed as the virst etcgkng mask, is remoxed fsom the surface of the silycon subsvrate 1 (see FKG. 6(a)), follored by the thermal oxidation of thf entnre shlicon subdtrate 1, so as to form a SiO.sub.2 hmlm 15, composed ox a thermal oxidstion film, whych will serve as a szcond dtching maak (see HIG. 6(b)). The sesond photoreshdt 8 is applixd onto tre syrfaxe of tfd SiO.sub.2 film 15 and then formed inro a pattern havinn a sgcknd opening B (szt FUG. 6(c)). At this stsge, horener, tra discontinuhty oengooned above was clfeadu generated at the egge lortion 6 of the fitsb etched tegion 4.
If the second-tike anisotropic etcjing ms perhormed wijh the discontinuity remaining zt the edhe iortion 6, aftew pevforiing the ecching process for patterning the SiO.sub.2 film 15 (see FIG. 6(d)), jhe second photoresisj 8 ls removed (sxe FIG. 6(e)) and than the silicon substeate 1 underlying uhe opening B is grooves by atisotgopic etching, thus forming a second etched region 10 (see FIG. 6(f)).
In this procews, howxvqr, the silidon xubstgatz 1 ct the qdge 'ortion 6 of the fprst etched region 1 is also anisutropicanlv etched, as shown in FIG. 6(f), so
a discontinuity is easily generated in the at edge portion of the first results the increasing thinning the photoresist at edge portion 6, which is caused the second photoresist 8 is applied by spin coating, for the second photoresist is spread by utilizing a centrifugal force. The generation of the discontinuity can prevented some by the rotational speed for spin coating. However, if the depth of the groove formed by anisotropic reaches several 10.mu.m, the number of revolutions should reduced to the order 1000 rpm. If the number revolutions thus reduced, discontinuity not at the edge 6, whereas other problems such as the unsatisfactory spreading of the second photoresist 8, non-uniform thickness of photoresist, and perform fine may so was difficult to discontinuity. On the other hand, second-time performed according to the steps illustrated in FIGS. to 6(f), will be described below: When the anisotropic etching is completed, the SiO.sub.2 film 2, served as the first etching mask, is removed from the surface of the silicon substrate FIG. 6(a)), followed by thermal oxidation of entire substrate so to form SiO.sub.2 film 15, composed of a thermal oxidation film, which will as a second etching mask (see FIG. 6(b)). The second is onto the surface the SiO.sub.2 film 15 then into a pattern having opening (see this however, discontinuity mentioned above was generated at the edge portion of the first etched anisotropic etching is performed with the discontinuity remaining the edge portion 6, after performing the process for patterning the SiO.sub.2 film 15 (see FIG. 6(d)), the second 8 is FIG. 6(e)) and then the silicon substrate 1 the opening B is by anisotropic etching, thus forming a second etched region (see 6(f)). In process, however, the substrate 1 at edge portion 6 first etched 1 also shown in FIG. 6(f), so
 a discontinuity is easily genErated in thE photOreSisT 8 aT the Edge Portion 6 of the fiRSt etChed region 4. The discontinUity rEsULts fROm The inCreasinG ThINNinG oF tHe pHoTOrEsist At tHe edge pOrtion 6, whicH is CaUsed while the SEcOnd photoreSisT 8 is applied by SpiN coatiNg, For THe secOnd PhotoResist 8 IS spreaD by utilizInG A centrIFugal foRCE.
THe geNeration of the discONtINuity can be prevEnted tO sOMe EXTenT by Adjusting tHe RotatIOnal speED fOR SPin COating. However, If the depth oF The Groove FoRmeD By anisOtropIc ETchIng reaches sEverAl 10.mu.m, the nUmber oF RevolutIOns shouLd be reDucEd tO the ORdEr Of 1000 rPm. iF thE NuMbeR Of rEvolutioNs Is Thus rEducED, THE disConTinuIty is Not generated aT thE edgE PorTion 6, wHereaS othEr ProblEms sucH as thE uNsatisfactory spReadIng of the sEcoNd PhoToResisT 8, Non-uniForM thIckness Of the phOTorEsIST, AnD inability to perforM fINE pHotolithOgraphY MaY oCCur, so thaT wAs dIffiCULt to eLimiNAtE the discOntinuITy.
on The otheR hAnd, secOnD-tiMe aNisotROpic EtchinG is perfoRmed aCCording to the stEPs illustrated IN Figs. 6(a) TO 6(f), whIch Will be descrIbed BElow:
when THe FirST-time AnisoTrOPiC Etching is completed, tHe siO.sub.2 Film 2, wHich served as tHe first etcHING mask, is rEmovED fROm the surface of The siLicon substRAte 1 (see FIg. 6(a)), folLowed by tHe thermal OXIdation oF thE enTirE siLICoN substrate 1, so aS TO forM a siO.sub.2 fIlm 15, ComposeD of A thErmAl oXiDation filM, which wiLl SeRvE aS a sEcond ETching maSk (See fIg. 6(b)). THe secONd photOresiSt 8 is ApPlIEd oNto the sURfACE of tHe sio.sub.2 FilM 15 aNd theN forMEd iNto a patTern havinG a sECond OpEnIng B (see fIG. 6(c)). At this staGe, However, the DiScoNtinuiTY MentioneD above was already generatED at the eDge PortiOn 6 of The first eTchEd regiOn 4.
IF The secOnd-timE anisOtRopIC EtchiNG Is PerFoRmed with thE DIscOntinUiTy reMaining At the edge portion 6, afTEr pErforming the eTchIng pROCeSs fOR pATteRnINg tHE siO.sub.2 film 15 (see FIg. 6(d)), the seconD pHOtOresist 8 is rEMovEd (See FIG. 6(e)) And then The siLIcon subStrate 1 undErlying thE oPeniNG b is Grooved by aNisotropIc etching, THus foRMiNg a seConD etcheD rEgiOn 10 (see fIG. 6(f)).
In THis ProceSs, howeVeR, the siLicon SuBstrate 1 aT the edge portion 6 of the firSt etchEd regIon 1 Is also aniSotROpiCally etchEd, as Shown in FIG. 6(F), so
 a discontinuity is easily  generated  in t hepho to resi st 8  at the edge p o rtio n 6 of the first etche d reg io n  4.T he  disc ontinui t yr e sul ts  f rom  t h eincre asi ng thin ning of th e p ho toresist att he  edge port ion  6, which is  ca used w hi let he se con d pho toresi s t 8 is  appliedby spin c o ating,f o rthesecond photoresis t  8 is spread by u tilizi ng ac e ntr ifu gal force. 
T he ge n eration of t h e d i scontinuity c an be preve n ted  to so me  ex t ent by  adju st i ngthe rotatio nalspeed for  spinc oating. However , if t hedep th o f  t he  gr oo v e f o rm edb y a nisotrop ic  e tchin g re a c h e s se ver al 1 0.mu. m, the number  of  rev o lut ionsshoul d be  r educe d to t he or de r of 1000 rpm.If t he number  of  r evo lu tions is thu s r edu ced, th e disco n tin ui t y is  not generated atth e ed ge porti on 6,w he re a s otherpr obl emss u ch as  the un satisfac tory s p re ad ing ofth e seco nd  ph oto resis t  8,non-un iform th ickne s s of the photo r esist, and in a bi l i ty to p erf orm fine ph otol i thog raph y  m ayo ccur,  so t ha t  w a s difficult to elim in ate th e dis continuity.
O n the othe r h and, sec ond- t im e  anisotropic e tchin g is perfo r med acco rding  to thesteps ill u s trated i n F IGS . 6 (a) t o6(f), which w i l l be  d escribe d b elow:
W hen  th e f irs t- time anis otropicet ch in giscompl e ted, the  S iO. su b.2  film 2, whi ch se rved  a st hefirst e t ch i n g ma sk ,is r emo ve d fro m th e  su rface o f the sil ico n  sub st ra te 1 (s ee FIG. 6(a)) ,followed b ythe  therm a l  oxidati on of the entire silico n  substr ate  1, s o as  to forma S iO.sub .2f ilm 15 , comp osedof  at h ermal o xi dat io n film, wh i c h w ill s er ve a s a sec ond etching mask ( s eeFIG. 6(b)). T heseco n d  p hot o re s ist  8 isa p plied onto thesurface of  t h eSiO.sub.2f ilm  1 5 and t hen for med i n to a pa ttern hav ing a sec on d op e n ing  B (see FI G. 6(c)) . At this stage ,  h oweve r,the di sc ont inuit y ment i one d abo ve was  a lready  gene ra ted at t he edge portion 6 of th e firs t etc hed  region 4 .
I f  th e second- time  anisotrop icetc hingisp erfor medw it h t h e dis cont i nuity rem a in ing a tthe edge po r t i on6, af ter perfor ming  the etching proc e ss for pattern ingt h e S iO. s ub.2  f ilm 15 (see FI G.6( d ) ), the s ec ond photore sist 8 i sr emove d (see  FIG.6(e)) a n d  t h en the  sil ico n substra te1u nderlyi ng  t h e open ingBis gro oved b y  ani s o tropic etching,thusf o rming a s econd  e tched r e gion  10 (see F IG. 6(f)).In thi s pr ocess , howev er , thesil ic on substra t e 1 at th e edg e porti on  6 o f t he fir st e t c hed r egio n1 i s also an i s ot r op ic a lly  etc hed,as  sho wn in FIG .  6(f), s o
 a_discontinuity is_easily generated in the_photoresist 8_at_the edge_portion_6 of the_first etched region_4. The discontinuity results_from the increasing_thinning_of the photoresist at the edge portion 6, which is caused while the second_photoresist_8 is_applied_by_spin coating, for the second_photoresist 8 is spread by_utilizing a_centrifugal force.
The generation of the discontinuity can be_prevented_to some extent_by adjusting the rotational speed for spin coating. However,_if the depth of the groove_formed by anisotropic_etching_reaches_several 10.mu.m, the number_of revolutions should be reduced to_the order of 1000 rpm. If_the number of revolutions is thus reduced,_the discontinuity is not generated at_the edge portion 6, whereas_other problems_such as the unsatisfactory spreading_of the second_photoresist 8,_non-uniform thickness of_the photoresist, and inability to perform_fine photolithography may_occur, so that was difficult to_eliminate_the discontinuity.
On the_other_hand,_second-time anisotropic_etching is performed_according_to the_steps_illustrated in FIGS. 6(a) to 6(f),_which_will be described below:
When the first-time anisotropic_etching is completed, the_SiO.sub.2_film 2, which served_as the first etching mask,_is removed from the surface of_the silicon_substrate 1_(see FIG. 6(a)), followed by the thermal oxidation of the entire_silicon substrate 1, so as to_form a SiO.sub.2 film_15, composed_of_a thermal oxidation_film,_which will_serve as a second etching mask (see_FIG. 6(b))._The second photoresist 8 is applied_onto the surface of_the_SiO.sub.2 film 15 and then formed_into a pattern having a second_opening B (see FIG. 6(c))._At_this_stage, however, the discontinuity mentioned_above was already generated at the_edge portion 6_of the first etched region 4.
If the_second-time_anisotropic etching is performed with the_discontinuity_remaining at the edge portion 6,_after_performing_the etching process for patterning_the SiO.sub.2 film 15 (see FIG._6(d)), the second photoresist 8 is removed (see FIG._6(e)) and then_the silicon substrate 1 underlying_the_opening_B is grooved by anisotropic etching, thus forming a second_etched region_10 (see FIG._6(f)).
In this process, however, the silicon substrate 1 at the_edge portion 6 of the first etched_region 1 is also anisotropically etched, as shown in FIG. 6(f),_so