Semiconductor device including protecting MOS transistor.

摘要

A zero-cross thyristor comprises an n-type sub­strate region (l05) surrounded by a p-type region (l06), a p-type base region (l03) formed in the n-type substrate region and surrounding an n-type inner region (l05′) of the n-type substrate region, and a p-type floating region (ll0) formed in the n-type inner region. An n-channel MOS transistor whose gate is connected to the floating region (ll0) is formed in the p-type base region (l03). A first p⁺-type diffusion region (lll) whose depth is less than that of the p-type base region is continuously formed in the p-type base region and the n-type inner region and a second p⁺-type diffusion region (ll2) whose depth is also less than that of the p-type floating region (ll0). The distance between the first and second diffusion regions is set to a predetermined value for preventing the breakdown of the gate insulating layer of the MOS transistor.