A tunnel field-effect transistor (FET) (TFET), in which the dominant carrier tunneling occurs in a direction that is in line with the gate electric field, shows great promise for sub-0.6-V operation. A detailed investigation, with the help of extensive device simulations, of the effects of a spacer-drain overlap on the device characteristics of such silicon TFET is reported in this paper. It is demonstrated that a supersteep subthreshold swing and a significantly reduced off-state current I\rm OFF can be achieved by appropriate designing of the spacer-drain overlap. An investigation of the influence of the drain potential on the device characteristics reveals that the absence of a tunnel-resistance limited region results in long-channel metal-oxide-semiconductor FET-like output characteristics for such a structure. Short-channel effects, such as drain-induced barrier lowering, are also greatly suppressed in it. Results of the investigation on the scaling properties of such devices are also reported. © 1963-2012 IEEE.