According to one embodiment, a semiconductor device of an embodiment includes a substrate, a metal plate having a main portion having a first width in a first direction and a second width in a second direction orthogonal to the first direction, a first semiconductor chip located between the metal plate and the substrate, the first semiconductor chip having a third width in the first direction and a fourth width in the second direction, and a second semiconductor chip located between the first semiconductor chip and the substrate, wherein the first width is smaller than the third width, and the second width is smaller than the fourth width.