A semiconductor device comprises a plurality of semiconductor chips; electrodes formed on circuit surfaces of said plurality of semiconductor chips; inner leads made of a metal foil and bonded at first ends thereof to the electrodes, outer leads each having a predetermined surface at a first end thereof bonded to a second end of at least one of the inner leads, and a sealing material sealing said plurality of semiconductor chips, the electrodes, the inner leads, and part of each of the outer leads. The semiconductor chips are laminated in such a manner that those surfaces of the semiconductor chips on which their respective circuits are formed are disposed in facing relation to each other. This provides a semiconductor device which is excellent in assembling efficiency.