A knowledge of subthreshold behavior in an insulated gate field-effect transistor (IGFET) is impOrtant for CircuitS with low leakage specifications. This paper discusses the effect of drain voltage on the subthreshold region as the channel length becomes shorter, the effect of substrate bias on both the shift in and the slope of the subthreshold curves, and the effect of temperature on the subthreshold current characteristics. It is shown that all these effects can be incorported into a simple one-dimensional model. © 1974, IEEE. All rights reserved.