Obtaining a structure comprised of first and second layers of a first semiconductor materials and a strain relief buffer (SRB) layer between the first and second layers, forming a sidewall spacer on the sidewalls of an opening in the second layer, and forming a third semiconductor material in the opening, wherein the first, second and third semiconductor materials are different. A device includes first and second layers of first and second semiconductor materials and an SRB layer positioned above the first layer. The second layer is positioned above a first portion of the SRB layer, a region of a third semiconductor material is in an opening in the second layer and above a second portion of the SRB layer, and an insulating material is positioned between the region comprised of the third semiconductor material and the second layer.