A 3D Monte Carlo (MC) device simulation model is developed for the treatment of discrete random dopant distribution in sub-100 nm MOSFET. The electron-ion (e-i) interaction model is based on a suitable description of long-range Coulomb interaction included by a particle-mesh (PM) calculation method and short-range interaction taken into account by a scattering mechanism. Attention is given to the correct definition of the short-range domain and scattering model. This new approach is validated by computing the low-field electron drift mobility in Si by means of MC simulation of 3D resistors in the doping concentration range of 10(15)-6.4 x 10(19) cm(-3). A good agreement is found between calculation and experimental data at 300 K. (C) 2002 Elsevier Science Ltd. All rights reserved.