A semiconductor device (1) is provided with: a first semiconductor chip (2) that is provided with first electrodes (21) on the surface; and an expanded semiconductor chip (3) which comprises a second semiconductor chip (31) and a resin expanded part (33) that is formed outwardly from at least one lateral surface of the second semiconductor chip, said expanded semiconductor chip (3) being provided with second electrodes (35) on the surface. The first semiconductor chip and the expanded semiconductor chip are arranged so that the surfaces on which the first electrodes and the second electrodes are formed face each other, and the first electrodes and the second electrodes are connected with each other. Among the second electrodes of the expanded semiconductor chip, those connected with the first electrodes are formed only on the resin expanded part.