Semiconductor device with multi-layered source/drain regions having different dopant concentrations and manufacturing method thereof

A method of forming a Fin Field-Effect Transistor (FinFET) device, the method comprising:

• forming a gate structure over a fin that protrudes above a substrate;
• forming a recess in the fin next to the gate structure;
• lining sidewalls and a bottom of the recess with a first semiconductor layer, wherein lining the sidewalls and the bottom of the recess comprises conformally forming the first semiconductor layer in the recess;
• changing a shape of the first semiconductor layer;
• and
• after changing the shape of the first semiconductor layer, filling the recess with a second semiconductor layer.

A Fin Field-Effect Transistor (FinFET) device comprising:

• a fin over a substrate;
• a first gate structure and a second gate structure over the fin;
• and
• a first source/drain region at least partially in the fin and between the first gate structure and the second gate structure, the first source/drain region comprising:
• a first semiconductor layer extending from an upper surface of the fin into the fin, wherein the first semiconductor layer is non-conformal, wherein a first end portion of the first semiconductor layer and a second end portion of the first semiconductor layer are proximate to the upper surface of the fin, and are thicker than other portions of the first semiconductor layer, wherein the other portions of the first semiconductor layer are closer to the substrate than the first end portion and the second end portion of the first semiconductor layer;
• and
• a second semiconductor layer over the first semiconductor layer, wherein the first semiconductor layer and the second semiconductor layer comprise a semiconductor material doped with a dopant, wherein a first dopant concentration of the dopant in the first semiconductor layer is lower than a second dopant concentration of the dopant in the second semiconductor layer.