US Patent 7468297 Method of manufacturing semiconductor device

A method of manufacturing semiconductor device comprising forms a first impurity diffusion region as a lower electrode of a capacitor in a first area of a semiconductor substrate by implanting impurities at a first dose; forms a second impurity diffusion region in a second area, at the end part of the semiconductor substrate, by implanting impurities at a second dose; and forms, by a thermal oxidation method, a capacitor insulation film having a first thickness on the first impurity diffusion region and forms an oxide film having a second thickness which is thicker than the first thickness on the second area.