Methods of making fins and fin field effect transistors (finfets)

Abstract

Methods of making fins and semiconductor structures containing fins are provided. The methods involve forming a multi-layer structure over a semiconductor substrate. The multi-layer structure comprises a first layer over the semiconductor substrate, a second layer over the first layer, and a third layer over the second layer. The method also comprises removing upper portions of the semiconductor substrate and portions of the multi-layer structure to form fins of the semiconductor substrate and portions of the multi-layer structure. Further, the method comprises selectively oxidizing the first layer while oxidization of the second layer and the third layer is less than the oxidization of the first layer. The oxidation can be performed before gap fill recess or after gap fill recess.