A semiconductor device includes a substrate having a logic region and a high-voltage (HV) region, a first gate structure on the HV region, a first epitaxial layer and a second epitaxial layer adjacent to one side of the first gate structure, a first contact plug between the first epitaxial layer and the second epitaxial layer, a third epitaxial layer and a fourth epitaxial layer adjacent to another side of the first gate structure, and a second contact plug between the third epitaxial layer and the fourth epitaxial layer. Preferably, a bottom surface of the first epitaxial layer is lower than a bottom surface of the first contact plug and a bottom surface of the third epitaxial layer is lower than a bottom surface of the second contact plug.