A semiconductor device includes a lead frame, a transistor, and an encapsulation resin. The lead frame includes a drain frame, a source frame, and a gate frame. The drain frame includes drain frame fingers. The source frame includes source frame fingers. The drain frame fingers and the source frame fingers are alternately arranged in a first direction and include overlapping portions as viewed from a first direction. In a region where each drain frame finger overlaps the source frame fingers as viewed in the first direction, at least either one of the drain frame fingers and the source frame fingers are not exposed from the back surface of the encapsulation resin.