Semiconductor device structure and method for forming the same

A method for forming a semiconductor device structure, comprising:

• forming a first gate stack and a second gate stack over a substrate, wherein the substrate has a base, a first multilayer stack, and a second multilayer stack over the base, the first gate stack wraps around the first multilayer stack, and the second gate stack wraps around the second multilayer stack;
• forming a first mask layer over a first sidewall of the first multilayer stack;
• forming a first stressor over a second sidewall of the second multilayer stack while the first mask layer covers the first sidewall of the first multilayer stack;
• removing the first mask layer;
• and
• forming a dielectric layer over the first stressor and the base, wherein the dielectric layer covers the first sidewall.

A method for forming a semiconductor device structure, comprising:

• forming a first gate stack and a second gate stack over a substrate, wherein the substrate has a base, a first multilayer stack, and a second multilayer stack over the base, the first multilayer stack and the second multilayer stack are separated by a gap, the first gate stack wraps around the first multilayer stack, and the second gate stack wraps around the second multilayer stack;
• forming a mask layer in the gap;
• forming a first stressor over a first sidewall of the first multilayer stack while the mask layer is in the gap, wherein the first sidewall faces away from the gap;
• removing the mask layer;
• and
• forming a dielectric layer partially over the first stressor and partially in the gap, wherein the dielectric layer in the gap covers a second sidewall of the first multilayer stack, and the second sidewall is opposite to the first sidewall.