The present invention provides a manufacturing method for a semiconductor device having epitaxial source/drain regions, in which a diffusion barrier layer of the source/drain regions made of epitaxial silicon-carbon or germanium silicon-carbon are added on the basis of epitaxially growing germanium-silicon of the source/drain regions in the prior art process, and the introduction of the diffusion barrier layer of the source/drain regions prevents diffusion of the dopant in the source/drain regions, thus mitigating the SCE and DIBL effect. The use of the diffusion barrier layer for the source/drain regions can also reduce the dosage of HALO implantation in the subsequent step, thus if HALO is performed before epitaxial growth of the source/drain regions, impact on the surfaces of the source/drain regions can be alleviated; if HALO is performed after epitaxial growth of the source/drain regions, the stress release effect of the epitaxial layer of the source drain/regions caused by the implantation can be reduced as much as possible.