MANUFACTURE OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To suppress short circuit of a transistor electrode by lightening the stepped form of an element isolating region, in a field shield element isolation where a sidewall oxide film part is made by thermal oxidation. SOLUTION: A gate oxide film 2 is made by thermally oxidizing a silicon semiconductor substrate 1, and next polycrystalline silicon 3 and an oxide film 4 are made in order. Next, this stacked film is patterned into the shape of a field shield electrode FS, and the sidewall of the field shield electrode 3 is thermally oxidized to form a sidewall thermal oxide film part 7. Next, a CVD oxide film 13 is stacked all over the semiconductor substrate 1, and next, the CVD oxide film 13 is etched, whereby a fanwise side wall oxide film 13 is made at the flank of the field shield electrode FS.