| CPC H01L 29/6656 (2013.01) [H01L 21/28518 (2013.01); H01L 29/0847 (2013.01); H01L 29/41791 (2013.01); H01L 29/45 (2013.01); H01L 29/4983 (2013.01); H01L 29/66545 (2013.01); H01L 29/66636 (2013.01); H01L 29/66795 (2013.01); H01L 29/7851 (2013.01)] | 20 Claims |

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1. A semiconductor structure, comprising:
a fin comprising a channel region and a source/drain region adjacent the channel region;
a gate structure wrapping over the channel region;
a multilayer gate spacer disposed along sidewalls of the gate structure;
a source/drain feature disposed over the source/drain region; and
a multilayer contact etch stop layer (CESL) disposed along sidewalls of the multilayer gate spacer and on the source/drain feature,
wherein the multilayer gate spacer comprises a low-k dielectric layer in contact with the sidewall of the gate structure and a first silicon sublayer over the low-k dielectric layer,
wherein the multilayer CESL comprises a second silicon sublayer in contact with the sidewall of the multilayer gate spacer and a nitrogen-containing sublayer over the second silicon sublayer.
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