Embodiments of the invention include nanowire and nanoribbon transistors and methods of forming such transistors. According to an embodiment, a method for forming a microelectronic device may include forming a multi-layer stack within a trench formed in a shallow trench isolation (STI) layer. The multi-layer stack may comprise at least a channel layer, a release layer formed below the channel layer, and a buffer layer formed below the channel layer. The STI layer may be recessed so that a top surface of the STI layer is below a top surface of the release layer. The exposed release layer from below the channel layer by selectively etching away the release layer relative to the channel layer.