We investigated the effect of nitrogen implantation on dichlorosilane-based WSix (DCS WSix)/P-doped Si stack gate electrode. DCS WSix was known to be susceptible to abnormal oxidation during oxidation at low temperature. The abnormal oxidation was attributed to tungsten oxidation during gate reoxidation, resulting in deformation of the gate electrode profile. Nitrogen implantation on DCS WSix effectively suppressed the abnormal oxidation of the silicide during gate reoxidation even at low temperature around 750 degrees C, due to its roles of amorphization of DCS WSix and oxidation retardation of the silicide. We also found that the additional nitrogen implantation did not degrade gate oxide integrity.