A semiconductor device includes a semiconductor element, a first lead including a mounting portion for the semiconductor element and a first terminal portion connected to the mounting portion, and a sealing resin covering the semiconductor element and a portion of the first lead. The mounting portion has a mounting-portion front surface and a mounting-portion back surface opposite to each other in a thickness direction, with the semiconductor element mounted on the mounting-portion front surface. The sealing resin includes a resin front surface, a resin back surface and a resin side surface connecting the resin front surface and the resin back surface. The mounting-portion back surface of the first lead is flush with the resin back surface. The first terminal portion includes a first-terminal-portion back surface exposed from the resin back surface, in a manner such that the first-terminal-portion back surface extends to the resin side surface.