A semiconductor device model based on a set of quantum mechanically de
rived hydrodynamic balance equations are presented. This model takes f
ull account of band nonparabolicity, in addition to its other useful f
eatures such as the explicit evaluation of momentum and energy relaxat
ion rates, in the form of frictional force and energy loss rate, withi
n the model, and inclusion of carrier-carrier interaction effects, suc
h as dynamical screening. Numerical results of one-dimensional device
simulations are presented and compared with parabolic approximations.