A variant tunnel field effect transistor structure called the binary tunnel field effect transistor (BTFET) for low voltage and near ideal switching characteristics is proposed. The BTFET relies on a binary tunneling distance (HIGH and LOW) for its operation to achieve a steep sub-threshold swing with a predicted range of 5 mV/dec. The transition of tunneling distance from HIGH to LOW state is a step-function of the gate voltage with the threshold voltage as a transition voltage. BTFET has a high on-current due to the high gate electric field and a large tunneling cross section area. An orientation dependent non-local band-to-band tunneling model was used to analyze the DC characteristics of the device. © 2010 The Japan Society of Applied Physics.