A method of manufacturing a semiconductor device according to an embodiment includes: forming a mask material having an opening on a surface of a silicon carbide layer; forming a trench in the silicon carbide layer using the mask material as a mask; performing first ion implantation for implanting carbon (C) into a bottom face of the trench using the mask material as a mask; forming a sidewall material on a side face of the trench; performing second ion implantation for implanting a p-type first impurity into the bottom face of the trench using the sidewall material as a mask; and performing heat treatment at 1600° C. or more.