Decreasing device dimensions will cause an increasing internal field strength in a semiconductor device. The average carrier energy is different from the thermal equilibrium value 3/2kT. Modification of current transport is considered on different levels of approximation. In a local approximation wederivea field‐dependent carrier mobility and temperature from a more general self‐consistent formulation. Numerical estimation of hot‐electron effects are given for a realisticn‐channel metal‐oxide‐semiconductor field‐effect transistor of various channel lengths. It is shown that both high‐field and field‐gradient effects will contribute.