A Physical Charge-Controlled Model for MOS Transistors

As MOS devices scale to submicron lengths, short-channel effects become more pronounced, and an improved transistor model becomes a necessary tool for the VLSI designer [10]. We present a simple, physically based charge-controlled model. The current in the MOS transistor is described in terms of the mobile charge in the channel, and incorporates the physical processes of drift and diffusion. The effect of velocity saturation is included in the drift term. We define a complete set of natural units for velocity, voltage, length, charge, and current. The solution of the dimensionless current-flow equations using these units is a simple continuous expression, equally applicable in the subthreshold, saturation, and "ohmic" regions of transistor operation, and suitable for computer simulation of integrated circuits. The model is in agreement with measurements on short-channel transistors down to 0 .351" channel length.