According to one embodiment, a method for manufacturing a semiconductor device is disclosed. The method can include performing a first heat treatment of a first film at a first temperature not less than 500° C. and not more than 900° C. in a first atmosphere including oxygen. The first film includes silicon and oxygen and is deposited on a semiconductor member including silicon carbide. The method can include performing, after the first heat treatment, a second heat treatment of the first film at a second temperature not less than 1200° C. but less than 1400° C. in a second atmosphere including nitrogen.