Patent ID: 7943446

Claim:
A method of producing a semiconductor device including forming gate electrodes of a plurality of transistors supplied with different voltages on a semiconductor substrate via a gate insulating film, comprising the steps of: forming said gate insulating film on said semiconductor substrate; forming a gate electrode layer containing an impurity on said gate insulating film; implanting an additional impurity at regions of said gate electrode layer for forming transistors where the electrical effective thickness required of said gate insulating film based on said voltage is relatively thin; and processing said gate electrode layer to form gate electrodes with concentrations of impurities differing for each transistor, wherein, a height of said gate insulating film is different between regions for forming transistors having relatively thin effective thicknesses of said gate insulating film and regions for forming transistors having relatively thick effective thicknesses of said gate insulating film, and said step of implanting the additional impurity comprises selecting the regions of the electrode layer in accordance with said height of said gate insulating film.