A semiconductor device includes a first semiconductor element, a first heat dissipation plate connected to the first semiconductor element, a sealing body that integrally holds the first semiconductor element and the first heat dissipation plate, and a first terminal that is electrically connected to the first semiconductor element and protrudes from the sealing body. The first heat dissipation plate has an insulating substrate, an inner conductor layer, and an outer conductor layer. The outer conductor layer is exposed on a first main surface of the sealing body. The first terminal protrudes from a first side surface adjacent to the first main surface of the sealing body. On the first main surface of the sealing body, at least one first groove extending in a direction along the first side surface is provided in a range located between the outer conductor layer and the first side surface.