A semiconductor device includes: a substrate; a semiconductor chip with a surface facing down mounted on the substrate; a reinforcement material provided on the substrate in a peripheral region of a region on which the semiconductor chip is mounted; and a heat sink coupled to the semiconductor chip via a highly thermally conductive material. The heat sink is disposed on the semiconductor chip and the reinforcement material by being coupled to the reinforcement material via an adhesive material, and is provided with an uneven area on a side coupled to the reinforcement material.