Current and capacitance characteristics of a metal-insulator-semiconductorstructure with an ultrathin oxide layer

By self-consistently solving the Schrodinger and Poisson equations, we have studied theoretically the current and capacitance characteristics of a met al-oxide-semiconductor structure consisting of an ultrathin oxide layer emb edded between an n-silicon substrate and n(+)-polycrystalline silicon gate. It has been shown that due to the finite doping level in the polycrystalli ne silicon gate and the complication of the energy sublevels in the accumul ation layer, self-consistent calculation of Schrodinger and Poisson equatio ns is of vital importance. Decreasing the oxide layer thickness drastically increases the conduction current density from the substrate to the polycry stalline silicon gate. The capacitance increases monotonically as a functio n of the gate bias, it gradually saturates. The theoretical results explain well our experimental data. (C) 2001 Academic Press.