It is an object of the present invention to provide an easily assemblable semiconductor device including a cover that covers a top of a case and is reliably fixed to the case defining an outline of the semiconductor device. A semiconductor device according to the present invention includes: a case defining an outline of the semiconductor device; a cover covering a top of the case; and a fastener mechanically fixing the cover to the case, a through-hole is formed in the cover, the case includes a projection inserted into the through-hole, and the fastener is attachable to the projection inserted into the through-hole of the cover from the outside of the cover and locks the projection upon the attachment to prevent the projection from falling off the through-hole.