A breakdown voltage of a clamp diode can be reduced while a leakage current is suppressed. A P− type diffusion layer is formed in a surface of an N− type semiconductor layer. An N+ type diffusion layer is formed in a surface of the P− type diffusion layer. A P+ type diffusion layer is formed adjacent the N+ type diffusion layer in the surface of the P− type diffusion layer. An N+ type diffusion layer is formed adjacent the P− type diffusion layer in the surface of the N− type semiconductor layer. There is formed a cathode electrode, which is electrically connected with the N+ type diffusion layer through a contact hole formed in an insulation film on the N+ type diffusion layer. There is formed a wiring (an anode electrode) connecting between the P+ type diffusion layer and the N+ type diffusion layer through a contact hole formed in the insulation film on the P+ type diffusion layer and a contact hole formed in the insulation film on the N+ type diffusion layer.