Hot electron transport in MOS transistors is investigated by means of coupled silicon/oxide Monte Carlo (MC) simulation. First, a new MC simulator able to handle simultaneously different materials is developed. Then, the impact of oxide transport on the gate current (I-G) is analyzed comparing different injection models with experiments. It is shown that oxide transport plays an important role on to when the gate voltage is below the drain voltage (V-GS < V-DS). In this condition, coupled silicon/oxide simulation (C-SIOX) is needed to quantitatively assess I-G. It is also shown that oxide scattering in the image force potential well does not significantly reduce I-G. Moreover, we propose a new injection model that empirically accounts for oxide scattering and that provides the same I-G of the C-SIOX model, but with the simulation of the silicon channel only, thus enabling a significant reduction of simulation time. (C) 2003 Elsevier Science Ltd. All rights reserved.