A semiconductor device manufacturing method is provided. The method includes forming a first, second and third films, forming a first mask pattern on the third film, forming a gate electrode by using the first mask pattern, forming a second mask pattern having an opening above a portion of the first mask pattern and a region adjacent to the gate electrode, and performing ion implantation by using the first and second mask patterns. The gate electrode formation includes etching the third film, etching the second film and overetching the second film by using a first, second and third processing gases. A first, second and third depositions formed on the sidewalls of the gate electrode in the third and second films etching and overetching, contain at least one of chlorine or bromine and do not contain fluorine.