Semiconductor device and method

A method comprising:

• forming a gate stack on a fin;
• etching the fin to form a recess in the fin adjacent the gate stack;
• dispensing semiconductor material precursors to form a first epitaxial layer in the recess;
• after dispensing the semiconductor material precursors, dispensing a dopant precursor to form an impurity layer on the first epitaxial layer;
• after dispensing the dopant precursor, resuming the dispensing of the semiconductor material precursors to form a second epitaxial layer on the impurity layer;
• and
• performing an anneal to diffuse at least a portion of the impurity layer into the first epitaxial layer and the second epitaxial layer.

A method comprising:

• forming a gate stack on a channel region of a substrate;
• patterning a recess in the substrate adjacent the channel region;
• growing a first epitaxial layer in the recess, the first epitaxial layer comprising a semiconductor material doped with gallium to a first concentration;
• growing a second epitaxial layer on the first epitaxial layer, the second epitaxial layer comprising the semiconductor material doped with gallium to a second concentration, the second concentration greater than the first concentration;
• and
• growing a third epitaxial layer on the second epitaxial layer, the third epitaxial layer comprising the semiconductor material doped with gallium to the second concentration, the third epitaxial layer grown at a higher epitaxial growth rate than the second epitaxial layer.