Semiconductor device and manufacturing method therefor

There is disclosed a semiconductor device comprising at least one semiconductor element, one chip mounting base being provided at least one first interconnection on one major surface thereof and at least one second interconnection on the other major surface thereof, and the semiconductor element being electrically connected to at least the one first interconnection and mounted on the one major surface, a sealing member being provided on the one major surface of the chip mounting base and covering the semiconductor element and the first interconnection, at least one third interconnection being provided on a surface of the sealing member, and at least one fourth interconnection being provided in the sealing member and the chip mounting base, and electrically connected to the first interconnection, the second interconnection, and the third interconnection.