A semiconductor device includes a metal substrate, semiconductor elements, wires, a control terminal, a main electrode terminal, a control substrate, a cover, a sealing resin, a case, and an insulator. The metal substrate includes a metal plate, an insulating layer formed on the top surface of the metal plate, and electrode patterns provided on the insulating layer. The semiconductor elements are secured to different ones of the electrode patterns by solder. The sealing resin seals the components within the case, such as the semiconductor elements. The insulator covers a portion of the surface of the insulating layer and at least a portion of the edge of each electrode pattern.