Abstract: A semiconductor device and a forming method thereof are provided. The semiconductor device includes a device layer including a front side and a back side opposite to each other, a bonding layer disposed on the back side of the device layer, and a carrier substrate underlying the bonding layer. The device layer includes source/drain (S/D) structures, semiconductor channel layers connecting the S/D structures, and a gate structure disposed between the S/D structures and around each of the semiconductor channel layers, where the back side is planar and includes the S/D structures and the gate structure.

Abstract: A semiconductor structure includes a channel structure, a gate structure, two source/drain features, and a plurality of inner spacers. The channel structure includes a plurality of channel features which are spaced apart from each other. The gate structure is disposed to surround the channel features. The source/drain features are disposed at two opposite sides of the channel structure such that each of the channel features interconnects the source/drain features. Each of the inner spacers is disposed to separate the gate structure from a corresponding one of the source/drain features. Each of the inner spacers includes an inner spacer body and a lateral nitrided portion. The lateral nitrided portion is in direct contact with the corresponding one of the source/drain features and has a nitrogen content greater than that of the inner spacer body.