Semiconductor structure

A semiconductor structure, comprising:

• a substrate;
• a first semiconductor layer over the semiconductor substrate in a Z-direction;
• a second semiconductor layer over and spaced apart from the first semiconductor layer in the Z-direction;
• source/drain features on opposite sides of the first semiconductor layer and the second semiconductor layer in an X-direction;
• rare earth oxide layers on top surfaces and bottom surfaces of the first semiconductor layer and the second semiconductor layer;
• and
• a gate structure wrapping around center portions of the first semiconductor layer, the second semiconductor layer, and the rare earth oxide layers, wherein the center portions of the rare earth oxide layers are in contact with the gate structure in the Z-direction.

A semiconductor structure, comprising:

• a substrate;
• semiconductor layers extending in an X-direction and over the substrate, wherein the semiconductor layers are spaced apart from each other in a Z-direction;
• source/drain features on opposite sides of the semiconductor layers in the X-direction;
• metal oxide layers covering top surfaces and bottom surfaces of the semiconductor layers;
• inner spacers between the metal oxide layers in the Z-direction;
• and
• a gate structure wrapping around the semiconductor layers and the metal oxide layers, wherein center portions of the metal oxide layers are in contact with the gate structure in the Z-direction.