Patent ID: 7192881

Claim:
A method, comprising: depositing a first silicon dioxide layer over a substrate comprising a line feature; heat treating said substrate to densify said first silicon dioxide layer; forming a first spacer layer over said densified first silicon dioxide layer; anisotropically etching said first spacer layer while using said densified first silicon dioxide layer as an etch stop layer to form first sidewall spacers adjacent to said line feature, during said anisotropically etching said first spacer layer, an upper sidewall portion of said line feature being exposed through said first sidewall spacers; and depositing a second silicon dioxide layer over said substrate, heat treating said substrate to density said second silicon dioxide layer, depositing a second spacer layer over said second silicon dioxide layer, and forming a second sidewall spacer adjacent to said first sidewall spacer by anisotropically etching said second spacer layer to expose said upper sidewall portion of said line feature.