We present 3-D analytical, scalable models for the threshold voltage roll-off, the subthreshold swing and the DIBL of undoped cylindrical Gate All Around (GAA) MOSFETs. The models are based on an analytical solution of the 3-D Poisson equation. Device geometry dependences are inherent to the models. Excellent agreement has been obtained with 3-D numerical simulations and experimental results. © 2007 Springer.