| 摘要 |
A semiconductor device includes a semiconductor substrate, a gate stack on the semiconductor substrate, and a stressor adjacent the gate stack and having at least a portion in the semiconductor substrate, wherein the stressor comprises an element for adjusting a lattice constant of the stressor. The stressor includes a lower portion and a higher portion on the lower portion, wherein the element in the lower portion has a first atomic percentage, and the element in the higher portion has a second atomic percentage substantially greater than the first atomic percentage.
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