Metal gate with PVD amorphous silicon layer having implanted dopants for CMOS devices and method of making with a replacement gate process

摘要

A semiconductor structure and method for making the same provides a metal gate on a silicon substrate. The gate includes a high dielectric constant on the substrate, and a physical vapor deposited (PVD) layer of amorphous silicon on the high k gate dielectric. The metal is then formed on the PVD amorphous silicon layer. Additional dopants are implanted into the PVD amorphous silicon layer. An annealing process forms silicide in the gate, with a layer of silicon remaining unreacted. The work function of the metal gate is substantially the same as a polysilicon gate due to the presence of the PVD amorphous silicon layer, while the additional doping of the PVD amorphous silicon layer lowers the resistivity of the gate electrode.