Semiconductor device and manufacturing method thereof

A method of forming a semiconductor device, comprising:

• forming a first fin structure protruding from a substrate;
• forming a second fin structure protruding from the substrate;
• forming a first gate stack crossing the first fin structure;
• forming a second gate stack crossing the second fin structure and parallel to the first gate stack, wherein the first fin structure has a first channel region under the first gate stack and a first source/drain region adjacent to the first channel region, and the second fin structure has a second channel region under the second gate stack and a second source/drain region adjacent to the second channel region;
• performing an ion implantation process to introduce impurities into the second source/drain region to form an implanted region in the second source/drain region such that the second source/drain region has a bottom surface at a different height than a bottom surface of the first source/drain region;
• prior to performing the ion implantation process, forming a first spacer layer extending along the first gate stack, the second gate stack, the first fin structure and the second fin structure;
• and
• after performing the ion implantation process, forming a second spacer layer on the first spacer layer.

A method of forming a semiconductor device, comprising:

• forming a first fin structure and a second fin structure on a substrate;
• forming a first gate stack and a second gate stack crossing the first fin structure and the second fin structure, respectively, wherein the first fin structure has a first channel region under the first gate stack and a first source/drain region adjacent to the first channel region, and the second fin structure has a second channel region under the second gate stack and a second source/drain region adjacent to the second channel region;
• performing an ion implantation process to introduce impurities into the second source/drain region to form an implanted region in the second source/drain region;
• forming a first epitaxy structure embedded in the first source/drain region and a second epitaxy structure embedded in the second source/drain region;
• prior to forming the first epitaxy structure and the second epitaxy structure, recessing the first source/drain region and the second source/drain region;
• and
• prior to recessing the first source/drain region and the second source/drain region, wherein performing the ion implantation process to introduce the impurities into the second source/drain region comprises introducing nitrogen atoms into the second source/drain region.