We have performed numerical simulations on Schottky barrier (SB) MOSFETs by solving the two-dimensional Poisson equation self-consistently with the Schrodinger equation. We have investigated the equilibrium charge distribution and the conduction energy bending in the inversion layer of the SB-MOSFETs. We have found that the quantum mechanical consideration is crucial for accurate estimation of the current in nano-scale SB-MOSFETs. We have also found that the threshold voltage for channel inversion increases when the channel length becomes shorter than about 30 nm, in contrast to conventional MOSFETs.