We propose a field‐effect tunnel transistor based on the metal–insulator transition. The principle of the switching is the metal–insulator transition, which occurs at the sheet resistanceRQ(∼h/e2=25.8 k&OHgr;). The modulation of the sheet resistance aroundRQby the control gates can be magnified by the phase transition. As a result, high transconductance and high current drivability more than 10 times greater than the ultimate silicon metal‐oxide‐semiconductor transistors are obtained. The device is a thin‐film silicon‐on‐insulator structure with dual gates, one on each side of the channel. A very thin granular metal film is deposited on the Si layer. Each metal island forms a Schottky contact with the Si layer, which is completely depleted. The electrons in the metal tunnel between the islands through the Si. The metal film can have a higher Coulomb gap and current drivability than is obtained with a single tunnel junction. A temperature of less than 1/20 of the Coulomb gap energy is required to reduce the leakage current by three orders of magnitude with the Coulomb blockade mechanism. Using the Wentzel–Kramers–Brillouin approximation, we calculated the tunneling probability between the islands and evaluated the sheet resistance of the metal film. Changing the gate voltage can modulate the sheet resistance in spite of the very narrow spacing between the islands. In the high resistance regime, the Coulomb blockade can operate and the resistance is three orders of magnitude higher than the bare tunnel resistance. In the ‘‘on’’ state, on the other hand, a very low sheet resistance of less than 1 k&OHgr; per square is obtained. ©1996 American Institute of Physics.