A semiconductor device includes a gate, a source region and a drain region that are co-doped to produce a strain in the channel region of a transistor. The co-doping can include having a source and drain region having silicon that includes boron and phosphorous or arsenic and gallium. The source and drain regions can include co-dopant levels of more than 1020 atom/cm3. The source region and drain region each can be co-doped with more boron than phosphorous or can be co-doped with more phosphorous than boron. Alternatively, the source region and drain region each can be co-doped with more arsenic than gallium or can be co-doped with more gallium than arsenic. A method of manufacturing a semiconductor device includes forming a gate on top of a substrate and over a nitrogenated oxide layer, etching a portion of the substrate and nitrogenated oxide layer to form a recessed source region and a recessed drain region, filling the recessed source region and the recessed drain region with a co-doped silicon compound. The co-doped silicon compound can include silicon, boron and phosphorous or can include silicon, arsenic and gallium. The co-doped silicon compound can be epitaxially grown in the recesses.