US Patent 9881998 Stacked nanosheet field effect transistor device with substrate isolation

Nanosheet FET devices having substrate isolation layers are provided, as well as methods for fabricating nanosheet FET devices with substrate isolation layers. For example, a semiconductor device includes a nanosheet stack structure formed on a substrate, which includes a rare earth oxide (REO) layer formed on the substrate, and a semiconductor channel layer disposed adjacent to the REO layer. A metal gate structure is formed over the nanosheet stack structure, and a gate insulating spacer is disposed on sidewalls of the metal gate structure, wherein end portions of the semiconductor channel layer are exposed through the gate insulating spacer. Source/drain regions are formed in contact with the exposed end portions of the semiconductor channel layer. A portion of the metal gate structure is disposed between the semiconductor channel layer and the REO layer, wherein the REO layer isolates the metal gate structure from the substrate.