Method of forming a germanium-containing finfet

Abstract

A method includes forming isolation regions in a semiconductor substrate, forming a first semiconductor strip between opposite portions of isolation regions, forming a second semiconductor strip overlying and contacting the first semiconductor strip, and performing a first recessing to recess the isolation regions. A portion of the second semiconductor strip over top surfaces of remaining portions of the isolation regions forms a semiconductor fin. A second recessing is performed to recess the isolation regions to extend the semiconductor fin downwardly, with an inter-diffusion region of the first semiconductor strip and the second semiconductor strip being exposed after the second recessing. The inter-diffusion region is then etched.