To obtain sufficient shape controllability at a gate electrode forming time without possibility of contaminating a recess surface before or after the step of forming a gate electrode.

A method for manufacturing a semiconductor device comprises the step of sequentially forming an SiO2 film 3 and an HSQ film 4 so as to cover the recess 5 formed on an active layer 2 on a semiconductor substrate 1. The method further comprises the steps of dry etching the film 3 and the film 4 under the condition in which the films 3 and 4 have substantially the same etching rate, and forming a straight gate opening 7. The method also comprises the steps of forming a gate electrode 8, then wet etching the films 3 and 4 under the condition in which the film 4 has sufficiently larger etching rate than that of the film 3, and removing only the film 4.