A semiconductor device with improved reliability and its manufacturing method is offered. The semiconductor device of this invention includes a semiconductor substrate, a pad electrode formed on the semiconductor substrate through an insulation layer made of silicon oxide, silicon nitride or the like, a supporting plate bonded to a top surface of the semiconductor substrate to cover the pad electrode and a via hole formed in the semiconductor substrate and extending from a back surface of the semiconductor substrate to the pad electrode, wherein an aperture of the via hole at a portion close to the pad electrode is larger than an aperture of the via hole at a portion close to the back surface of the semiconductor substrate.