According to one embodiment, a method for manufacturing a semiconductor device is disclosed. The method can include a first process of causing a stacking fault of a first semiconductor layer to expand. The first semiconductor layer includes silicon carbide and a first element and is provided on a base body including silicon carbide. The first element includes at least one selected from the group consisting of N, P, and As. The method can include a second process of forming a second semiconductor layer on the first semiconductor layer after the first process. The second semiconductor layer includes silicon carbide and the first element. The method can include a third process of forming a third semiconductor layer on the second semiconductor layer. The third semiconductor layer includes silicon carbide and a second element. The second element includes at least one selected from the group consisting of B, Al, and Ga.