A semiconductor device manufacture method has the steps of: (a) forming an interface layer of SiO or SiON on the surface of an active region of a silicon substrate; (b) forming a high dielectric constant gate insulating film such as HfSiON having a dielectric constant higher than that of silicon oxide, above the interface layer; (c) forming a gate electrode of polysilicon above the high dielectric constant gate insulating film; (d) passivating the substrate surface at least before or after the high dielectric constant gate insulating film is formed; (e) forming an insulated gate electrode structure by patterning at least the gate electrode and the high dielectric constant gate insulating film; and (f) forming source/drain regions in the active region on both sides of the insulated gate electrode structure. The semiconductor device has the high dielectric constant insulating film having a dielectric constant higher than that of silicon oxide.