A semiconductor device comprising: A substrate comprising a gate electrode formed over a channel region of the substrate, and a recessed source interface and a recessed drain interface formed on the substrate at opposite sides of the gate electrode; a first spacer and a second spacer formed on opposite sidewalls of the gate electrode, wherein a portion of the recessed source interface extends laterally beneath the bottom surface of the first spacer, and a portion of the recessed drain interface extends laterally beneath the bottom surface of the second spacer; a source region comprising a first epitaxial region formed over the recessed source interface, and a first cap layer formed over the first epitaxial region, wherein a portion of the first cap layer is formed between the first epitaxial region and the bottom surface of the first spacer; and a drain region comprising a second epitaxial region formed over the recessed drain interface, and a second cap layer formed over the second epitaxial region, wherein a portion of the second cap layer is formed between the second epitaxial region and the bottom surface of the second spacer, characterized in that the first and second epitaxial regions (531, 532) each comprises silicon and carbon doped with phosphorus, wherein the first and second epitaxial regions (531, 532) each comprises silicon having a carbon concentration in the range of 0.5 atomic % to 4 atomic %, anda phosphorus concentration in the range of 9E19 cm-3 to 3E21 cm-3, and wherein each of the first and second cap layers (541, 542) is a phosphorous doped silicon cap layer having a phosphorus concentration in the range of 8E19 cm-3 to 3E21 cm-3. a gate electrode formed over a channel region of the substrate, and a recessed source interface and a recessed drain interface formed on the substrate at opposite sides of the gate electrode; a first spacer and a second spacer formed on opposite sidewalls of the gate electrode, wherein a portion of the recessed source interface extends laterally beneath the bottom surface of the first spacer, and a portion of the recessed drain interface extends laterally beneath the bottom surface of the second spacer; a source region comprising a first epitaxial region formed over the recessed source interface, and a first cap layer formed over the first epitaxial region, wherein a portion of the first cap layer is formed between the first epitaxial region and the bottom surface of the first spacer; and a first epitaxial region formed over the recessed source interface, and a first cap layer formed over the first epitaxial region, wherein a portion of the first cap layer is formed between the first epitaxial region and the bottom surface of the first spacer; and a drain region comprising a second epitaxial region formed over the recessed drain interface, and a second cap layer formed over the second epitaxial region, wherein a portion of the second cap layer is formed between the second epitaxial region and the bottom surface of the second spacer, a second epitaxial region formed over the recessed drain interface, and a second cap layer formed over the second epitaxial region, wherein a portion of the second cap layer is formed between the second epitaxial region and the bottom surface of the second spacer, characterized in that the first and second epitaxial regions (531, 532) each comprises silicon and carbon doped with phosphorus, wherein the first and second epitaxial regions (531, 532) each comprises silicon having a carbon concentration in the range of 0.5 atomic % to 4 atomic %, anda phosphorus concentration in the range of 9E19 cm-3 to 3E21 cm-3, and wherein each of the first and second cap layers (541, 542) is a phosphorous doped silicon cap layer having a phosphorus concentration in the range of 8E19 cm-3 to 3E21 cm-3.