Patent ID: 7163871

Claim:
An oxidation method of a semiconductor substrate having an STI region, comprising the steps of: etching a semiconductor region to form a trench; preparing dichloroethylene (DCE); and subjecting an exposed inside upper end portion of the trench to halogen oxidation with the dichloroethylene and oxygen, whereby a thickness of an oxide film at a corner portion of the semiconductor region adjacent to said upper end portion of the trench is greater than a thickness of said oxide film at other portions of the trench, the halogen oxidation being carried out at a temperature between 850 and 950° C. in an atmosphere within a furnace, by controlling a concentration of the DCE within a range between 0.45 and 1.97% by weight, to thereby render a stress imposed on the upper corner portion of the trench to less than 100 MPa.