To provide a technique capable of increasing the cooling efficiency of a semiconductor device.

This device is provided with a wiring board 1, a semiconductor chip 2 which is mounted on a mounting surface of the wiring board 1 by using a face down method, and a heat-dissipating member 3, which is formed in a plane size greater than that of the semiconductor chip 2 and fixed on the back of the semiconductor chip 2. In this case, a first space region 9A of a chip fixing surface side of the heat-dissipating member 3 and a second space region 9B on the opposite surface side of the chip fixing surface side are connected continuously via a paths 8. The first spatial region 9A is regulated by the wiring board 1, the semiconductor chip 2 and the heat-dissipating member 3. The paths 8 are constituted of penetrating holes 8A or notched parts, which are formed in the heat-dissipating member 3.