We present an approach to the simulation of ultrasmall semiconductor devices based on Brownian motion of the carriers described by the Langevin equation. It follows the trajectories of individual particles in real space but does not require the computational effort of a full Monte Carlo simulation. This method is particularly useful for modeling very small devices where individual impurities and carriers must be considered, and the dynamics need to be treated atomistically, in a full‐scale three‐dimensional simulation. ©1996 American Institute of Physics.