Methods of forming field effect transistors having t-shaped gate electrodes using carbon-based etching masks

Abstract

Methods of forming field effect transistors include forming a first electrically insulating layer comprising mostly carbon on a surface of a semiconductor substrate and patterning the first electrically insulating layer to define an opening therein. A trench is formed in the substrate by etching the surface of the substrate using the patterned first electrically insulating layer as an etching mask. The trench is filled with a gate electrode. The first electrically insulating layer is patterned in an ambient containing oxygen. This oxygen-containing ambient supports further oxidation of trench-based isolation regions within the substrate when they are exposed by openings within the first electrically insulating layer.