Method for forming an isolation region in a semiconductor device and resulting structure using a two step oxidation process

Abstract

A method for forming an element isolation film of a semiconductor device and the semiconductor device. A pad insulator is constructed on a semiconductor substrate. An over-etching process is performed to recess the semiconductor substrate to a predetermined depth while giving a pad insulator pattern. After an insulator spacer is formed at the side wall of the pad insulator pattern, the exposed region of the semiconductor substrate is thermally oxidized to grow an oxide which is, then, removed to form a recess. An element isolation film is formed in the recess by break-through field oxidation and high temperature field oxidation. The element isolation film thus obtained can prevent the field oxide “ungrowth” phenomenon and at the same time mitigate the field oxide thinning effect as well as improve the properties of the gate oxide.