A semiconductor device includes a package part having a semiconductor element sealed in resin, a plurality of first leads each having an outer portion extending from a first side of the package part, and a plurality of second leads each having an outer portion extending from a second side of the package part. A combined bottom surface area of the outer portions of the plurality of first leads is greater than a combined bottom surface area of the outer portions of the plurality of second leads. The semiconductor device also includes a heat dissipation plate provided on the bottom surface of the package part and connected to at least one of the plurality of second leads.