The present invention provides a semiconductor device of a double-side mounting structure including a circuit board and a plurality of semiconductor chips arranged and joined together on the opposite surfaces of the circuit board, wherein in an area in which the semiconductor chip 31 mounted on the top surface of the circuit board 2 overlaps with the semiconductor chip 32 mounted on the bottom surface of the circuit board 2, a recess portion 21 (or a protruding portion 22) is formed in the surfaces of the circuit board 2.