Manufacturing technique for a semiconductor device having a first MISFET of an n channel-type and a second MISFET of a p channel type, including forming a first insulating film composed of a silicon oxide film or a silicon oxynitride film on a semiconductor substrate for forming a gate insulating film of the respective MISFETs; depositing metal elements on the first insulating film; forming of a silicon film on the first insulating film for the forming of a gate electrode of the respective MISFETs; and producing the respective gate electrodes by patterning the silicon film. The depositing of the metal films on the first insulating film is such that there is produced in the vicinity of the interface between the gate electrode and the gate insulating film a surface density of the metal elements within a range of 1×1013 to 5×1014 atoms/cm2.