To make a semiconductor device, which has a semiconductor structure called a CSP (Chip Size Package), into a fan-out terminal structure and thin in thickness.

A lower insulating film 1 made of epoxy resin etc., is provided on a top surface of a base plate 31 made of copper foil. Then the semiconductor construct 2 is mounted on a plurality of semiconductor construct mounting regions on a top surface of the lower insulating film 1 with an adhesion layer 3 interposed therebetween. A sealing film 28 made of epoxy resin etc., is formed on the top surface of the lower insulating film 1 including the semiconductor construct 2. The base plate 31 is removed. Therefore, the completed semiconductor device does not have the base plate 31 and the semiconductor device wherein an arrangement area for an electrode for external connection is larger than the plane size of the semiconductor construct 2 (Fan-out) can be made thin.