Semiconductor structure and method for manufacturing the same

A semiconductor structure, comprising:

• a substrate;
• nanostructures over the substrate and spaced apart from each other in a Z-direction;
• a gate structure extending in a Y-direction and wrapping around middle portions of the nanostructures;
• source/drain features on opposite sides of the gate structure in an X-direction and attached to the nanostructures in the X-direction;
• and
• inner spacers between side portions of the nanostructures in the Z-direction, wherein each of the inner spacers comprises:
• a soft core layer;
• and
• a hard liner layer wrapping around the soft core layer, wherein the hard liner layers separate the core layers from the nanostructures, the gate structure, and the source/drain features.

A method for manufacturing a semiconductor structure, comprising:

• forming a fin over a substrate, wherein the fin comprises first semiconductor layers and second semiconductor layers alternating stacked in a Z-direction;
• forming a dummy gate structure extending in a Y-direction and over the fin;
• forming gate spacers on sidewalls of the dummy gate structure in an X-direction;
• forming source/drain trenches in the fin and on opposite sides of the dummy gate structures in the X-direction;
• removing side portions of the first semiconductor layers through the source/drain trenches to form gaps between the second semiconductor layers in the Z-direction and direct under the gate spacers;
• forming first liner layers partially filling the gaps;
• forming core layers partially filling spaces in the gaps and the first liner layers;
• forming second liner layers filling remaining spaces in the gaps;
• forming P-type source/drain features in the source/drain trenches;
• and
• replacing the dummy gate structure and the first semiconductor layers with a gate structure wrapping around the second semiconductor layers.