A semiconductor device including a stacked assembly. The stacked assembly includes a metal substrate, a stacked substrate mounted on the metal substrate and having an electrode pattern, a semiconductor element mounted on the stacked substrate, and a lead frame interconnection electrically connecting the semiconductor element and the electrode pattern. The lead frame interconnection includes a first bonding portion in contact with the semiconductor element, a second bonding portion in contact with the electrode pattern, and an interconnect portion connecting the first and second bonding portions. At least one of the first bonding portion and the second bonding portion is wider than the interconnect portion.