Abstract 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 I G 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.