It is an object of the present invention to provide a semiconductor device that has sufficient insulation properties between a screw and a heat dissipation plate, and is smaller and less costly. A semiconductor device of the present invention includes the following: a housing containing a semiconductor element; a heat dissipation plate disposed on a bottom surface of the housing, and provided to partly extend beyond the housing to reach the outside; an electrode electrically connected to the semiconductor element, and provided to partly protrude from the housing to the outside in parallel with the heat dissipation plate; and a screw with which an exposed portion of the electrode, protruding from the housing is joined to a busbar. The heat dissipation plate has a thickness lack portion in a location of the heat dissipation plate, the location at least facing the screw, the location being on a screw side.