nFET device and method for fabricating same

A method for fabricating an nFET device, comprising:

• providing a substrate structure, wherein the substrate structure comprises a semiconductor substrate and at least one gate structure formed on the semiconductor substrate;
• forming openings in the semiconductor substrate on opposite sides of each gate structure;
• growing, by epitaxy, a phosphorus-doped epitaxial silicon layer in the openings;
• performing a secondary phosphorus ion implantation process on the phosphorus-doped epitaxial silicon layer;
• and
• forming a heavily phosphorus-doped epitaxial silicon layer by performing a laser annealing process on the phosphorus-doped epitaxial silicon layer, thereby forming source and drain structures,
• wherein the heavily phosphorus-doped epitaxial silicon layer extends from a surface of the phosphorus-doped epitaxial silicon layer into the phosphorus-doped epitaxial silicon layer, and wherein the source and drain structure comprises the phosphorus-doped epitaxial silicon layer and the heavily phosphorus-doped epitaxial silicon layer,
• wherein the heavily phosphorus-doped epitaxial silicon layer contains trisilicon tetraphosphide and has a thickness in a range of 20 nm to 30 nm.