The effect of a triple metal-gate (TMG) on the performance and on the ambipolar current in a TMG vertical tunnel field-effect transistor with triple metal-gate (TMG-TFET) is investigated using technology computer-aided design simulation. The TMG-TFET is designed to tackle the performance as well as the ambipolar current, simultaneously, by modulating the TMG parameters-the work function of the TMG and/or the length of each MG-that have critical impacts on the energy-band diagrams of the channel region. The tempered on-/off-current ratio of 10(8) and the steep average subthreshold slope of 43.5 mV/decade at a power supply voltage of 0.5 V are ascribed to the formation of an energy barrier in the channel by the optimal device parameters. It is found that two main flaws in a conventional (single-material gate) TFET, which are the degraded on-state current and the ambipolar current, can be successfully controlled by adjusting the TMG structure.