To provide a semiconductor device which improves the reliability.

A semiconductor device 1 includes: a wiring board 10; a first semiconductor chip 21 mounted on the wiring board 10; a second semiconductor chip 22 which is mounted on the wiring board 10 and has a heating value smaller than the first semiconductor chip 21; and a heat radiation plate 30 disposed above the first semiconductor chip 21 and the second semiconductor chip 22. The heat radiation plate 30 thermally connects with the first semiconductor chip 21, and an opening 30X is formed at a position facing the second semiconductor chip 22. An entire upper surface of the second semiconductor chip 22 is exposed from the opening 30X of the heat radiation plate 30.