The stress distribution in the Si channel regions of a SiC source/drain and stressed silicon nitride liner NMOSFETs with various widths were studied using 3D simulations. The mobility enhancement was found to be dominated by the tensile stress along the transport direction. Stress along the width direction was found to have the least effect on the drain current. The compressive stress along the vertical direction perpendicular to the gate oxide (Szz) contributes significantly to the mobility enhancement and cannot be neglected in NMOSFETs with a width between 0.05 and 1 mm. The impact of width on performance improvements such as the drive current gain was also analyzed. (C) 2008 Elsevier B. V. All rights reserved.