by including a thin "work function metal" layer between the high-κ dielectric and the main metal. This layer is thin enough that the total work function of the gate is influenced by both the main metal and thin metal work functions (either due to alloying during annealing, or simply due to the incomplete screening by the thin metal). The threshold voltage thus can be tuned by the thickness of the thin metal layer. High-κ dielectrics are now well studied, and their defects are understood. HKMG processes exist that do not require the metals to experience high temperature anneals; other processes select metals that can survive the annealing step. Insulator As devices are made smaller, insulating layers are made thinner, often through steps of thermal oxidation or localised oxidation of silicon (LOCOS). For nano-scaled devices, at some point tunneling of carriers through the insulator from the channel to the gate electrode takes place. To reduce the resulting leakage current, the insulator can be made thinner by choosing a material with a higher dielectric constant. To see how thickness and dielectric constant are related, note that Gauss's law connects field to charge as: with Q = charge density, κ = dielectric constant, ε0 = permittivity of empty space and E = electric field. From this law it appears the same charge can be maintained in the channel at a lower field provided κ is increased. The voltage on the gate is given by: with VG = gate voltage, Vch = voltage at channel side of insulator, and tins = insulator thickness. This equation shows the gate voltage will not increase when the insulator thickness increases, provided κ increases to keep tins / κ = constant (see the article on high-κ dielectrics for more detail, and the section in this article on gate-oxide leakage). The insulator in a MOSFET is a dielectric which can in any event be silicon oxide, formed by LOCOS but many other dielectric materials are employed. The generic term for the dielectric is gate dielectric since the dielectric lies directly below the gate electrode and above the channel of the MOSFET. Junction design The source-to-body and drain-to-body junctions are the object of much attention because of three major factors: their design affects the current-voltage (I-V) characteristics of the device, lowering output resistance, and also the speed of the device through the loading effect of the junction capacitances, and finally,