An implantation of phosphorus is used in tungsten polycide gate process, and the effects of implantation on the reduction of resistance and characteristics of GOI (Gate Oxide Integrity) were investigated. The sheet resistance of gate electrode decreases with increase of phosphorus implant dose and energy as increase of grain size. The depletion effects of gate polysilicon at reverse biases were found in unimplanted tungsten polycide gate due to the out-diffusion of dopant atoms in buffer polysilicon layers during activation anneals. However, the depletion effects of gate polysilicon were effectively suppressed by the implantation of phosphorus. The lifetime of gate oxide was degraded several orders of magnitude for the high-energy implanted samples. Therefore, there is optimum energy for phosphorus implantation into gate electrode ro Improve the resistance of tungsten polycide gate electrode and the depletion effects of gate polysilicon.