Abstract: The present disclosure includes a method of plasma etching a trench having rounded top corners in a silicon substrate. One embodiment includes the following general steps: a) providing a semiconductor structure comprising a hard masking layer, overlying a silicon substrate; b) plasma etching through said hard masking layer and any additional underlying layers overlying said silicon substrate using at least one plasma feed gas which does not provide polymer deposition on surfaces of said semiconductor structure during etching; where said plasma etching exposes a face of said silicon substrate; and c) plasma etching at least a first portion of a trench into said silicon substrate using reactive species generated from a feed gas comprising a source of fluorine, a source of carbon, a source of hydrogen, and a source of high energy species which provide physical bombardment of said silicon substrate.