Method for fabricating semiconductor device having bulb-shaped recess gate

摘要

A method for fabricating a semiconductor device includes etching a portion of a substrate to form a recess. A polymer layer fills a lower portion of the recess. Sidewall spacers are formed over the recess above the lower portion of the recess. The polymer layer is removed. The lower portion of the recess is isotropically etching to form a bulb-shaped recess.