A semiconductor device exhibiting good characteristics by sustaining the dielectric constant of a High-K insulating film in a high state, and a process for fabricating a semiconductor device in which the dielectric constant of the High-K insulating film can be sustained in a high state. The semiconductor device comprises a silicon substrate, a gate electrode layer, and a gate insulating film interposed between the silicon substrate and the gate electrode layer. The gate insulating film is a high dielectric constant (high-k) film produced by nitriding a mixture of a metal and silicon. Since the High-K film itself is a nitride, generation of SiO2 can be prevented.