The normal and reverse short-channel effect of LDD MOSFET's with lateral channel-engineering (pocket or halo implant) has been investigated. An analytical model is developed which can predict V th as a function of L eff , V DS , V BS , and pocket parameters down to 0.1-μm channel length. The new model shows that the V th , roll-up component due to pocket implant has an exponential dependence on channel length and is determined roughly by (N p ) 1/4 L p . The validity of the model is verified by both experimental data and two-dimensional (2-D) numerical simulation. On the basis of the model, a methodology to optimize the minimum channel length L min is presented. The theoretical optimal pocket implant performance is to achieve an imin approximately 55-60% that of a uniform-channel MOSFET without pocket implant, which is a significant (over one technology generation) improvement. The process design window of pocket implant is analyzed. The design tradeoff between the improvement of short-channel immunity and the other device electrical performance is also discussed.