INSULATED GATE TYPE OF TRANSISTOR, AND ITS MANUFACTURE

PROBLEM TO BE SOLVED: To prevent the insulation breakage of the gate insulating film, at the gate electrode polysilicon extracting-out part at the terminus of a trench top. SOLUTION: An insulated gate type of transistor has a first conductive type of a first semiconductor layer and a second conductive type of a second semiconductor layer 2 a first conductivity type of third semiconductor layer stacked in order, and a trench 5 reaching the first semiconductor layer via a second semiconductor layer 2 from the surface of the third semiconductor layer, and a gate insulating film 6 and a gate electrode 7 made on the surface of the trench 5, and the electric conductivity between the third semiconductor layer and the first semiconductor layer is controlled by the voltage applied to the gate electrode 7. In this case, the thickness of the prescribed part of the gate insulating film 5 in the trench 5 is made larger than that of the other section of the trench.