A semiconductor device according to an embodiment is a semiconductor device in which a semiconductor chip mounted on a chip mounting part is sealed by resin and a first member is fixed to a chip mounting surface side between a peripheral portion of the semiconductor chip and a peripheral portion of the chip mounting part. Also, the first member is sealed by the resin. Also, a length of the first part of the chip mounting part in the first direction is larger than a length of the semiconductor chip in the first direction, in a plan view.