After the coupling between the longitudinal and transverse components of channel electron motion is considered, the coupled Schrodinger-Poisson equations have been self-consistently solved. The results demonstrate that channel electron velocity can largely affect the channel surface potential of nanometer n-MOSFET once the ballistic transport ensures the velocity higher than 1 x 10(7) cm/s. Self-consistent calculations clearly illustrate that a larger channel electron velocity leads to a larger change in the channel surface potential. In addition, the relative change in the channel surface potential caused by such a coupling depends on both acceptor concentration and gate voltage. These results suggest that such a coupling should be considered in the channel surface potential model of nanometer n-MOSFET when the ballistic transport ensures the velocity higher than 1 x 107 cm/s. (c) 2007 Elsevier Ltd. All rights reserved.