Remote Coulomb scattering in metal–oxide–semiconductor field effect transistors: Screening by electrons in the gate

The effect of screening of remote Coulomb scattering (RCS) by free electrons in the polycrystalline silicon (polysilicon) gate of a metal–oxide–semiconductor transistor has been analyzed. We have completed a previous model of RCS by adding the effects of the screening by electrons in the gate assuming a Thomas–Fermi dielectric function to take into account the response of the gate. A Monte Carlo simulator has been included in this model, in addition to phonon scattering, surface-roughness scattering, and Coulomb scattering due to substrate impurities. Using this Monte Carlo simulator, we have evaluated mobility curves for different values of the oxide thickness. Although the RCS effect is certainly weakened by the screening, it is still quite important for very thin oxide layers (Tox⩽1 nm), and therefore should be taken into account.