| 摘要 |
A semiconductor device is provided. The semiconductor device comprises a substrate, a gate structure, a spacer, a first poly-SiGe layer being boron-doped and a second poly-SiGe layer being boron-doped. The substrate has two openings and the gate structure is disposed on the substrate between the openings. The spacer is disposed on the sidewalls of the gate structure and above a portion of the openings. The first poly-SiGe layer is disposed on the surface of the openings in the substrate. The second poly-SiGe layer is disposed on the first poly-SiGe layer, and the top of the second poly-SiGe layer is higher than the surface of the substrate. Moreover, the boron concentration in the first poly-SiGe layer is lower than that in the second poly-SiGe layer.
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