A semiconductor device has a first MOS transistor formed on first active region of the first conductivity type, having first gate electrode structure, first source/drain regions, recesses formed in the first source/drain regions, and semiconductor buried regions buried and grown on the recesses for applying stress to the channel under the first gate electrode structure, and a second MOS transistor formed on second active region of the second conductivity type, having second gate electrode structure, second source/drain regions, and semiconductor epitaxial layers formed on the second source/drain regions without forming recesses and preferably applying stress to the channel under the second gate electrode structure. In a CMOS device, performance can be improved by utilizing stress and manufacture processes can be simplified.