In this paper, analytical models of subthreshold current and slope for asymmetric four-terminal double-gate (DG) MOSFETs are presented. The models are used to study the subthreshold characteristics with asymmetry in gate oxide thickness, gate material work function, and gate voltage. A model for the subthreshold behavior of three-terminal DG MOSFETs is also presented. The results of the models show excellent match with simulations using MEDICI. The analytical models provide physical insight which is helpful for device design. © 2008 IEEE.