A semiconductor device comprising a substrate is disclosed. The substrate comprises: a well of type one; a first doped region of type two, provided in the well of type one; a well of type two, adjacent to the well of type one; a first doped region of type one, doped in the well of type two; and a second doped region of type two, provided in the well of type one and the well of type two, not touching the first doped region of type two. The substrate comprises no isolating material provided in a current path formed by the first doped region of type two, the well of type one, the well of type two and the first doped region of type one.