US Patent 11588052 Sub-Fin isolation schemes for gate-all-around transistor devices

Sub-fin isolation schemes for gate-all-around (GAA) transistor devices are provided herein. In some cases, the sub-fin isolation schemes include forming one or more dielectric layers between each of the source/drain regions and the substrate. In some such cases, the one or more dielectric layers include material native to the gate sidewall spacers, for example, or other dielectric material. In other cases, the sub-fin isolation schemes include substrate modification that results in oppositely-type doped semiconductor material under each of the source/drain regions and in the sub-fin. The oppositely-type doped semiconductor material results in the interface between that material and each of the source/drain regions being a p-n or n-p junction to block the flow of carriers through the sub-fin. The various sub-fin isolation schemes described herein enable better short channel characteristics for GAA transistors (e.g., employing one or more nanowires, nanoribbons, or nanosheets), thereby improving device performance.