Patent ID: 6232171
Filing Date: 2001-05-15
Classification: H01L

Abstract:
A method for fabricating a semiconductor device containing an elongated trench, said process comprising the following steps:(a) forming an elongated trench into a substrate, said elongated trench having a sidewall which defines said elongated trench inside said substrate;(b) forming a filler oxide layer by using a filler oxide to fill said elongated trench;(c) etching said filler oxide layer down to a depth, to reveal an upper portion of said sidewall above said filler oxide layer;(d) depositing a nitride layer, then using anisotropic dry etching to form a nitride sidewall spacer on said upper portion of said sidewall;(e) removing said filler oxide layer while leaving said nitride sidewall spacer in place by selective etching, to reveal a lower portion of said sidewall;(f) using said nitride sidewall spacer as a mask to cause said lower portion of said sidewall to be subject to an oxidation reaction; and(g) removing said oxidized lower portion of said sidewall to form a bottle-shaped elongated trench having an enhanced sidewall surface at said lower portion.