According to one or more embodiments of the present invention, a method for forming a fin structure for a semiconductor device includes forming a fin. The method further includes recessing a first portion of the fin to form a recess in the fin. The method further includes forming a channel region in the first portion of the fin. The method further includes forming an extension region on a second portion of the fin, and wherein defects are collected within the extension regions from the channel region in the first portion of the fin.