In this paper, by comparison of Drift-Diffusion and Monte Carlo simulation results, we investigate the impact of Coulombic scattering in atomistic device simulations and its contribution to the random dopant induced intrinsic parameter fluctuations in nano-CMOS devices. By introducing ionised impurity scattering directly into the Monte Carlo simulations through the full impurity potential, we resolve the contribution of the variation in scattering on the random dopant induced current variation. In comparison, Drift-Diffusion simulations are only able to capture the corresponding electrostatic effects. This approach is first demonstrated for the simple case of a single scattering centre in the channel of a MOSFET and then used to compare current variations in a set of devices with atomistic doping. (c) 2005 Elsevier Ltd. All rights reserved.