We have performed a fully 2-dimensional (2D) Poisson, Schrodinger and continuity equations modeling of nanometer gate HEMTs. For the electron density n(x,y) in the channel we use the discrete levels obtained from the Schrodinger equation and the corresponding 1 D density of states (DOS), so that a fully quantum representation of n is obtained. The threshold voltage reduction Delta V-T we obtain at small V-DS is in very good agreement with experimental values. By comparison with our classical calculations (a subset of our model) we deduce that quantum effects are not important for the calculation of Delta V-T. However quantum effects become increasingly important as V-GS increases beyond V-T at small V-DS The deviation between classical and quantum values in the current are of the order of 40 - 80% depending oil the device. As V-DS increases and reaches saturation this percentage deviation decreases but its absolute value (in mA/mm) increases. These effects become more acute as the gate length becomes shorter. (c) 2007 Elsevier Ltd. All rights reserved.