Transconductance Enhancement Dependence on the Channel Length of CESL-Strained nMOSFETs

Stress is distributed unequally along channels by both uniaxial and biaxial stressors. This study investigated channel-length-related performance enhancement by using contact etching stop layer (CESL) as the stressor. Devices with low tensile (L.T.) and high tensile (H.T.) stresses use CESLs with different thicknesses on nMOSFETs. Results indicate that transconductance enhances the shortest channel in H.T. devices compared with L.T. devices. The threshold voltage difference between L.T. and H.T. nMOSFETs verifies the high stress in H.T. nMOSFETs. However, this threshold voltage difference cannot verify the considerable decrease in the threshold voltage of the shortest channel of H.T. devices compared with L.T. devices.