A general solution for the electrostatic potential in an atomic-thin-body field-effect transistor (ATB-FET) geometry is presented. The effective electrostatic scaling length λeff is extracted from the analytical model, which cannot be approximated by the lowest order eigenmode as traditionally done in SOI-MOSFETs. An empirical equation for the scaling length that depends on the geometry parameters is proposed. It is shown that, even for a thick SiO2 back oxide, λeff can be improved efficiently by a thinner top oxide thickness and, to some extent, with high-kappa; dielectrics. The model is then applied to a self-consistent simulation of graphene nanoribbon (GNR) Schottky-barrier FETs (SB-FETs) at the ballistic limit. In the case of GNR SB-FETs, for a large λeff, the scaling is limited by the conventional electrostatic short-channel effects. On the other hand, for a small λeff, the scaling is limited by direct source-to-drain tunneling. A subthreshold swing below 100 mV/dec is still possible with a sub-10-nm gate length in GNR SB-FETs. © 2006 IEEE.