| abstract |
A method for manufacturing a semiconductor device includes: recessing a semiconductor fin to form a recess, wherein the semiconductor fin protrudes higher than isolation regions on both sides of the semiconductor fin; and performing a first epitaxial step to grow A first epitaxial layer extending into the recess. The first epitaxial step is performed by using a first process gas. The first process gas includes a silicon-containing gas, a silane, and a phosphorus-containing gas. The first epitaxial layer has a first percentage of phosphorus atoms. The method further includes performing a second epitaxial step to grow and extend a second epitaxial layer into the recess and above the first epitaxial layer. The second epitaxial step is performed using a second process gas. The second process gas includes a silicon-containing gas, a silane, and a phosphorus-containing gas. The second epitaxial layer has a second phosphorus atomic percentage higher than the first phosphorus atomic percentage. |