The behaviors of the hot-electron gate and substrate currents in very short channel devices were studied. For a test device with electrical channel length of 0.14 μm, the hot-electron substrate current can be detected at 0.9-V drain voltage which is lower than the silicon band gap. The gate current can be measured at 2.35-V drain voltage, which is lower than the oxide-silicon energy barrier for electrons. These measurements support the quasi-thermal-equilibrium approximation and suggest that the hot-electron-induced problems cannot be eliminated in future VLSI MOSFET's of arbitrarily short channels by reducing the drain bias below some constant critical energies. An empirical relationship between the effective electron temperature and the field is found to be Te = 9.05 × 10–3E.