In this work a quasi-analytical physical model for the accurate prediction of the potential of GAA nanowire transistors with an arbitrary regular polygon as a cross section is developed. Two case studies concerning triangular and square cross-sections are particularly investigated and analyzed. The model is then extended to the transport direction; general expressions for the natural length are derived and validated by means of two- and three-dimensional numerical device simulations. Basic design guidelines, using an original analytical expression of the natural length, for robust electrostatic design are proposed, to predict the minimum technological gate length able to assure immunity to the SeEs. ©2009 IEEE.