Semiconductor device

A semiconductor device comprises:

• a semiconductor substrate;
• a plurality of gate stack structures disposed on a top surface of the semiconductor substrate;
• a SiGe epitaxial structure disposed between two adjacent gate stack structures;
• a plurality of doped regions;
• a silicide region in contact with a top surface and a sidewall of the SiGe epitaxial structure and top surfaces of first portions of the plurality of doped regions, wherein the silicide region comprises a non-linear profile;
• and
• a semiconductor feature partially overlapped with the SiGe epitaxial structure in a direction perpendicular to the top surface of the semiconductor substrate.

A semiconductor device comprises:

• a substrate;
• a plurality of dielectric layers over the substrate;
• a plurality of interfacial layers between the plurality of dielectric layers and the substrate;
• a plurality of gate electrodes disposed over the plurality of dielectric layers comprising:
• a plurality of metal layers;
• and
• a plurality of work function metal layers surrounding bottoms and sidewalls of the plurality of metal layers;
• and
• a source/drain epitaxial layer disposed in the substrate and between two adjacent gate electrodes;
• and
• a semiconductor feature vertically sandwiched between the source/drain epitaxial layer and the substrate.