Semiconductor device with surge protection circuit capable of preventing current leakage

Abstract

A semiconductor device has a surge protection circuit electrically connected to a signal input terminal and including a diode and a transistor. The diode has its cathode region constituted of an ndiffusion layer, an nepitaxial layer, an n-type diffusion layer and an ndiffusion layer. The ndiffusion layer is electrically connected to a conductive layer and formed at a main surface of a semiconductor substrate. The ndiffusion layer constitutes, together with a p-type diffusion layer, a pn junction where Zener breakdown occurs, and the pn junction with the Zener breakdown occurring therein is distant from a field oxide film. Then, the semiconductor device with the surge protection circuit without suffering from current leakage and thus normally operating can be achieved.