A semiconductor device of an embodiment includes a silicon carbide layer including a first plane and a second plane; a trench including a first side face, a second side face, and a bottom face; a first silicon carbide region of a first-conductivity type; a second silicon carbide region of a second-conductivity type; a third silicon carbide region of the second-conductivity type sandwiching the trench with the second silicon carbide region; a sixth silicon carbide region of the second-conductivity type being in contact with the second side face and the bottom face; a gate electrode; and an insulating layer between the gate electrode and the second silicon carbide region, in which a portion of the first side face being in contact with the first silicon carbide region includes a first, second, and third region, and inclination angle of the second region is shallower than those of the first and third regions.