INSULATED GATE SEMICONDUCTOR DEVICE

摘要

In a semiconductor device having a trench type insulated gate structure, in the case where a drift layer (2) of an n<-> conduction type has a high carrier concentration, when a high voltage is applied between a drain and a source in such a manner that a channel is not formed, the electric field strength of an insulator layer (9) below the trench type insulated gate is increased, thus causing breakdown. The withstand voltage of the semiconductor device is limited by the breakdown of the insulator layer (9), and it is difficult to realize high withstand voltage. Thus, a field relaxation semiconductor region (1) of a conduction type opposite to the conduction type of the drift layer (2) is formed within the drift layer (2) below the insulator layer (9) in the trench of the trench type insulated gate semiconductor device. Also, the thickness of a bottom portion of the insulator layer (9) provided in the trench of the trench type insulated gate semiconductor device is made significantly greater than the thickness of a lateral portion thereof.