Method of manufacturing semiconductor device, and semiconductor device

摘要

A gate insulating film is formed on a substrate. Next, a gate electrode film is formed on the gate insulating film. A mask film is formed on a portion of the gate electrode film. The gate electrode film is selectively removed by etching using the mask film as a mask. A gate sidewall film is formed so as to be in contact with the lateral surfaces of the mask film and the gate electrode film. The mask film is formed of a laminated film in which at least a first film, a second film and a third film are laminated in this order. The second film has a higher etching selectivity ratio than that of the third film with respect to the gate sidewall film. The third film has a higher etching selectivity ratio than that of the second film with respect to the gate electrode film.