A quasi 2D semianalytical model for the potential profile in hetero and homojunction tunnel FETs is developed and compared with full-quantum simulation data. It will be shown that the pure analytical solution perfectly matches the k⋅p data at high VDS. However, a coupling with the numerical solution of the 1D Poisson equation in the transverse direction is necessary at low VDS, in order to properly describe the charge density in equilibrium with the drain contact. With such an approach we are able to correctly predict the potential profile for both the linear and saturation regimes.