The invention prevents a pad electrode for external connection of a semiconductor device from being damaged. An electronic circuit, a first pad electrode connected to the electronic circuit, and a second pad electrode connected to the first pad electrode are formed on a semiconductor substrate. A first protection film is formed, covering the first pad electrode and having an opening on the second pad electrode only. A wiring layer is further formed, being connected to the back surface of the first pad electrode through a via hole penetrating the semiconductor substrate and extending from the via hole onto the back surface of the semiconductor substrate.