A semiconductor device includes: a bottom plate having an upper surface and a lower surface, wherein the upper surface comprises an outer peripheral part and an inside part that is enclosed by the outer peripheral part and that protrudes more upward than the outer peripheral part; a frame joined to the upper surface of the bottom plate and comprising a first through-hole that penetrates the frame; a plate jointed to the outside or inside surface of the frame, the plate comprising a second through-hole that penetrates the plate in a same direction as that of the first through-hole, a thickness of the plate being greater than a thickness of the frame; a lead terminal inserted into the first through-hole and the second through-hole; a fixing member provided in the second through-hole and fixing the lead terminal; and a semiconductor element fixed to the inside part.