US Patent 9502265 Vertical gate all around (VGAA) transistors and methods of forming the same

An embodiment method includes forming a nanowire extending upwards from a substrate, wherein the nanowire includes: a bottom semiconductor region; a middle semiconductor region over the bottom semiconductor region; and a top semiconductor region over the middle semiconductor region. The method also includes forming a dielectric layer around and extending over the nanowire and forming a chemical mechanical polish-stop (CMP-stop) layer within the dielectric layer using an implantation process. After forming the CMP-stop layer, the dielectric layer is planarized.