SEMICONDUCTOR DEVICE AND MANUFACTURING METHOD THEREOF

PROBLEM TO BE SOLVED: To provide a semiconductor device which has high withstand voltage and can be manufactured at low cost, and a manufacturing method thereof. SOLUTION: The semiconductor device 100 has a structure in which a trench insulting gate transistor 30 is formed on the inside of a semiconductor substrate 20, a LOCOS oxide film 40 is formed on the outside semiconductor substrate 20 so as to be separated from an outermost trench insulating gate TG1, a second conductivity-type semiconductor region 50 is formed from the lower part of the outermost trench insulating gate TG1 to the lower part of the LOCOS oxide film 40, the second conductivity-type semiconductor region 50 consists of a first concentration region 51 for covering a corner portion TG1c from the lower part of the outermost trench insulating gate TG1 and a second concentration region 52 for covering the lower part of the LOCOS oxide film 40, the second concentration region 52 has an impurity concentration set lower than the impurity concentration of the first concentration region 51, and the second concentration region 52 has a diffusion depth set shallower than the diffusion depth of the first concentration region 51. COPYRIGHT: (C)2009,JPO&INPIT