Example embodiments relate to methods for forming a semiconductor device. One example method includes forming a device structure on a substrate, where the device structure includes a device layer stack that includes a bottom device sub-stack that includes at least one bottom channel layer and a top device sub-stack that includes at least one top channel layer, a sacrificial gate structure extending across the device layer stack, and bottom source/drain structures on opposite ends of at least one bottom channel layer. The method also includes forming an opening exposing the top device sub-stack, wherein forming the opening includes etching the sacrificial gate structure, forming a cut through the top device sub-stack by etching back the top device sub-stack from the opening and, subsequent to forming the cut, forming a functional gate stack on the at least one bottom channel layer.