The lower end of a resin wall is bonded to a radiating plate, and a lead is fixed so as to extend through the resin wall. After a semiconductor chip is bonded thereto, a resin lid is put to seal the semiconductor chip. Recessed parts for burying the lower end of the resin wall are formed on the side parts of the radiating plate, and protruding parts are further provided within the recessed parts. The lead has holes formed on the package outer part and the resin wall inner part. The loading surface of the semiconductor chip is finished with silver plating, and the package exterior and the lead are plated with gold. The shape fitted to the resin wall is imparted to the resin lid, and the resin lid is further formed into a vertically plane symmetric shape.