US Patent 10141310 Short channel effect suppression

A method of fabricating a semiconductor device includes forming a plurality of isolation features on a semiconductor substrate, thereby defining a first set of semiconductor features, performing an etching process on the first set of semiconductor features such that larger semiconductor features are etched deeper than smaller semiconductor features, after the etching process, forming anti-punch-through features on surfaces of the exposed features of the first set of semiconductor features, forming a semiconductor layer over the anti-punch-through features, and forming transistors on the semiconductor layer of each of the features of the first set of semiconductor features.