The threshold voltage Vth, of lightly doped drain (LDD) and non-LDD MOSFET’s with effective channel lengths down to the deep-submicrometer range has been investigated. Experimental data show that in the very-short-channel length range, the previously reported exponential dependence on channel length and the linear dependence on drain voltage no longer hold true. We use a simple quasi-two-dimensional model, taking into account the effects of gate oxide thickness, source/drain junction depth, and channel doping, to describe the accelerated Vth roll-off and the nonlinear drain voltage dependence. Relative to non-LDD devices, LDD devices have a smaller dependence of Vth on channel length due to their lower drain-substrate junction built-in potentials. LDD devices also show less Vth dependence on drain voltage because the LDD region reduces the effective drain voltage. Based on consideration of the short-channel effects, it is shown that the minimum acceptable length is equal to (0.0035 — 0.005) Xj1/3Tox micrometer (Xjin pm, T0xin Å).