Method for manufacturing semiconductor device

摘要

The method for manufacturing a semiconductor device according to the invention includes forming a thick silicon oxide film uniformly in a trench. Argon ions or the like implanted obliquely into the trench to form an ion implanted damaged region selectively in the portion of the silicon oxide film on the trench sidewall utilizing the shadowing effects of the oblique ion implantation. The silicon oxide film is wet etched to selectively remove the silicon oxide film in the ion implanted damaged region utilizing the etching rate difference, wherein the etching rate is faster in the damaged region than in the undamaged region. As a result, a thick residual oxide film is formed on the bottom and the lower sidewall portion of the trenchwithout causing any bird's beak.