Abstract: A method of manufacturing a semiconductor device includes, in this order: preparing a bottom plate having an upper surface and a lower surface, wherein the upper surface includes 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, and wherein the lower surface of the bottom plate includes a reference part and a recess positioned above the reference part, at least a part of the recess being disposed directly below the outer peripheral part; joining a frame member to the outer peripheral part of the bottom plate, a linear expansion coefficient of the frame member being smaller than a linear expansion coefficient of the bottom plate; and fixing a semiconductor element to the inside part of the bottom plate.