US Patent 7385244 Flash memory devices with box shaped polygate structures

A method for forming an improved etching hardmask oxide layer in a polysilicon etching process including providing a planarized semiconductor wafer process surface including adjacent first exposed polysilicon portions and exposed oxide portions; selectively etching through a thickness portion of the exposed oxide portions; thermally growing an oxide hardmask layer over the exposed polysilicon portions to form oxide hardmask portions; exposing second exposed polysilicon portions adjacent at least one oxide hardmask portion; and, etching through a thickness portion of the second exposed polysilicon portions.