US Patent 7402867 Semiconductor device

In a semiconductor device, a plurality of first diffusion regions of a first conductive type are formed on a diffusion layer well of the first conductive type. A plurality of second diffusion regions of a second conductive type are formed on the diffusion layer well of the first conductive type. An impurity concentration of each of the plurality of first and second diffusion regions is desirably higher than that of the diffusion layer well. The plurality of first diffusion regions are connected to a first common node as an anode and the plurality of second diffusion regions are connected to a second common node as a cathode.