Semiconductor device and manufacturing method thereof

Disconnection and deterioration in step coverage of wirings are prevented to offer a semiconductor device having higher reliability. A pad electrode is formed on a surface of a silicon die. A via hole penetrating the silicon die is formed from a back surface of the silicon die to the pad electrode. A wiring layer disposed on the back surface of the silicon die runs through the via hole and is electrically connected with the pad electrode. The wiring layer covers a convex portion of silicon on the back surface of the silicon die. A solder ball is formed on the wiring layer on the convex portion of silicon.