Patent ID: 6960530

Claim:
A method of reducing an aspect ratio of a trench, comprising the steps of: forming a trench in a substrate; forming a conformal first insulating layer on a surface of the trench; forming a conformal second insulating layer on the first insulating layer; forming a conformal third insulating layer on the second insulating layer; anisotropically etching the first, second and third insulating layers to form a remaining first insulating layer on a sidewall of the trench, a remaining second insulating layer on the remaining first insulating layer and a remaining third insulating layer on the remaining second insulating layer; and performing an etching procedure with an etchant to remove the remaining third insulating layer at a third etching rate, part of the remaining second insulating layer at a second etching rate and part of the remaining first insulating layer at a first etching rate; wherein the third etching rate is greater than the second etching rate and the second etching rate is greater than the first etching rate.