Semiconductor device

It is an object to provide a technique allowing for suppression of the height of a protrusion from the surface of a semiconductor module. A semiconductor device includes: a semiconductor module having a first groove; a Belleville washer having a recess in an outer surface and a protrusion on an inner surface; and a screw passing through the hole of the Belleville washer and the first groove of the semiconductor module to fasten the semiconductor module and an attached body. A head of the screw is accommodated in the recess of the Belleville washer, and at least portion of the protrusion of the Belleville washer is accommodated in the first groove of the semiconductor module.