Abstract: An input protection circuit comprises an internal circuit and an input terminal, between which a pair of rectifying devices are interposed with polygonal diffusion regions of one and the other conduction types, which diffusion regions are formed longer along the width thereof orthogonal to the direction of current flow in the wiring than along the direction of current flow. The width of the contacts between said wiring and said diffusion regions is greater than the width of the wiring not having the contacts, thereby achieving a high electrostatic breakdown voltage.