A semiconductor device includes a first case part, a second case part coupled to the first case part to provide a case, a semiconductor module disposed within the case closer to the second case part than to the first case part, and a plate interposed between the first case part and the semiconductor module. The plate is a thermal conductor, that is a material having thermal conductivity, to transfer heat generated by the semiconductor module to the case where the heat can dissipate to the outside of the semiconductor device.