US Patent 10991800 Method for FinFET LDD doping

A semiconductor device includes a substrate, an isolation structure over the substrate, a fin over the substrate and the isolation structure, a gate structure engaging a first portion of the fin, first sidewall spacers over sidewalls of the gate structure and over a second portion of the fin, source/drain (S/D) features adjacent to the first sidewall spacers, and second sidewall spacers over the isolation structure and over sidewalls of a portion of the S/D features. The second sidewall spacers and the second portion of the fin include a same dopant.