A comprehensive investigation into the various mechanisms that limit the accuracy of channel length extraction techniques for lightly doped drain (LDD) MOSFET's is presented. Analytic equations are derived to quantify the sensitivity of the extraction techniques to the geometry effect and bias dependence of the n- source and drain resistance. The analytic approach is supplemented and verified by exercising channel length extraction algorithms on current-voltage characteristics obtained from rigorous numerical simulations of a variety of LDD MOSFET's. The analyses clearly show that low gate overdrives and consistent threshold voltage measurements are required to accurately extract the metallurgical channel length. The analytic equations can be used to project the limitations of channel length extraction methods for future submicrometer LDD MOSFET's. © 1986 IEEE.