The effects of titanium and cobalt silicidation of the polysilicon gate in MOS capacitors on the electrical properties of the gate oxide are investigated. For the titanium polycide gate the value of the flat-band voltage is about 20 to 30 mV higher than for the polysilicon gate. A similar difference is observed in the value of the barrier height at the polycide/oxide interface from the Fowler-Nordheim characteristics. This phenomenon is explaind by postulating that phosphorus outdiffusion occurs from the polysilicon during the titanium silicidation process. For the cobalt polycide gate, no such differences with respect to the polysilicon gate are observed.