Dual work function metal gate CMOS transistors by Ni-Ti interdiffusion

In this letter, we present dual work function metal gate complementary metal-oxide semiconductor (CMOS) transistors with thin SiO2 gate dielectric fabricated through the interdiffusion of nickel and titanium. The threshold voltage of the n-MOS devices is determined solely by Ti, while the threshold voltage of the p-MOS devices is determined by the Ni-rich alloy of Ti and Ni. The advantage of this new approach is that low threshold voltages for surface-channel n-MOS and p-MOS transistors can be achieved simultaneously. At the same time, the integrity of the gate dielectric is preserved since no metal has to be etched from the surface of the gate dielectric. With gate depletion eliminated, these transistors exhibit high inversion charge and drive current.