Short-channel MOSFET VT-VDScharacteristics model based on a point charge and its mirror images

Short-channel MOS transistordV_{T}/dV_{DS}characteristics are expressed by an analytic function of fundamental device parameters. The expression is derived from a simple model of short-channel MOS transistors in threshold condition, which is based on a point charge and its mirror images. With this expression,dV_{T}/dV_{DS}is found to be proportional to1/L^{2}-1/L^{4}, whereLis channel length. Following factors are also found, wherein the source and drain junction depth effect is only logarithmic ondV_{T}/dV_{DS}characteristics,dV_{T}/dV_{SUB}anddV_{T}/dV_{DS}are closely related in short-channel MOS transistors, and short-channel effects are expected to be smaller in MOS transistors on SOS than on bulk silicon, due to a large number of Si/sapphire interface states. This model is simple, and it can be applied to short-channel MOS transistor designing and circuit simulations.