The open question whether excess noise is due to hot electrons or not is addressed for the first time by solving the full Langevin Boltzmann equation. Not only the bulk case is analyzed but also devices. In contrast to the well-known Monte Carlo method this new approach allows the investigation of the spatial origin of the terminal current noise. It is shown, that excess noise in devices is mainly due to cold or warm electrons. The contribution of hot electrons in a velocity saturation region is found to be negligible. This corroborates previous findings based on the less accurate impedance field method. (c) 2006 Elsevier Ltd. All rights reserved.