A fin field-effect transistor (FinFET) includes a substrate and a fin structure over the substrate. The fin structure comprises a lightly doped source and drain (LDD) region uniformly beneath a top surface and sidewall surfaces of the fin structure, the LDD region having a depth less than about 25 nm. Another FinFET includes a substrate and a fin structure over the substrate. The fin structure comprises a lightly doped source and drain (LDD) region, and a top surface of the fin structure has a different crystal structure from a sidewall surface of the fin structure. A method of making a FinFET includes forming a fin structure on a substrate. The method further includes performing a pulsed plasma doping on the fin structure to form lightly doped drain (LDD) regions in the fin structure.