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.