A semiconductor device includes a metal substrate including a metal base plate, an insulating sheet located on the metal base plate, and a wiring pattern located on the insulating sheet, and a semiconductor element located on the metal substrate. The semiconductor element is sealed with a molding resin. The molding resin extends to side surfaces of the metal substrate. On the side surfaces of the metal substrate, the insulating sheet and the wiring pattern are not exposed from the molding resin, whereas the metal base plate includes a projecting portion exposed from the molding resin.