We demonstrate a novel power Si/4H-SiC heterojunction tunneling transistor (HETT) on the basis of theoretical analysis and experimental results. The HETT is an insulated gate drive device and has a unique switching mechanism. In the off-state, the heterojunction barrier prevents current flow between the Si source region and the 4H-SiC drift region. In the on-state, the width of the heterojunction barrier is controlled by the gate bias to allow tunneling current to flow. The HETT has a zero channel length structure that is more independent of channel mobility compared with a conventional 4H-SiC MOSFET. As a result, the HETT is expected to have low on-resistance. A HETT was fabricated with n+-type polycrystalline silicon on an n--type 4H-SiC epitaxial wafer for power devices. The fabricated HETT shows a low specific on-resistance of 6.8 mcm2 (at Jd=500 A/cm2).