A semiconductor device includes a first gate electrode formed in a first region on a semiconductor substrate with a first gate insulating film sandwiched therebetween; and a second gate electrode formed in a second region on the semiconductor substrate with a second gate insulating film sandwiched therebetween. The first gate insulating film includes a first high dielectric constant insulating film with a first nitrogen concentration and the second gate insulating film includes a second high dielectric constant insulating film with a second nitrogen concentration higher than the first nitrogen concentration.