Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device comprising:

• forming a first-conductivity-type well of a first conductivity type and a second-conductivity-type well of a conductivity type opposite to the first conductivity type in a silicon substrate;
• stacking a first high-dielectric-constant insulating film and a first cap dielectric film above the silicon substrate;
• removing at least the first cap dielectric film from above the second-conductivity-type well and leaving the first cap dielectric film and the first high-dielectric-constant insulating film above the first-conductivity-type well;
• stacking a second high-dielectric-constant insulating film and a second cap dielectric film above the silicon substrate so as to cover the remaining first high-dielectric-constant insulating film and first cap dielectric film;
• removing the second cap dielectric film disposed above the first-conductivity-type well;
• and
• conducting a plasma nitriding treatment and annealing for fixing nitrogen to cause an element included in the first cap dielectric film to diffuse into the first high-dielectric-constant insulating film disposed above the first-conductivity-type well and to cause an element included in the second cap dielectric film to diffuse into the second high-dielectric-constant insulating film disposed above the second-conductivity-type well.