A simplified method to calculate the band bending and subband energies is e
mployed to investigate quantum mechanical effects (QME's) in MOS structure
inversion layer. The subband structure and the two-dimensional (2-D) densit
y-of-states in semi-classical and quantum mechanical cases art: then calcul
ated. The well-known band gap widening model is analyzed through a density-
uf-states point of view and a new scheme to analysis and modeling QME's in
MOS inversion layer is proposed.