Disclosed are flat/vertical type vacuum field transistor (VFT) structures, which adopt a MOSFET-like flat or vertical structure so as to increase the degree of integration and can be operated at low operation voltages at high speeds. The flat type comprises a source and a drain, made of conductors, which stand at a predetermined distance apart on a thin channel insulator with a vacuum channel therebetween; a gate, made of a conductor, which is formed with a width below the source and the drain, the channel insulator functioning to insulate the gate from the source and the drain; and an insulating body, which serves as a base for propping up the channel insulator and the gate. The vertical type comprises a conductive, continuous circumferential source with a void center, formed on a channel insulator; a conductive gate formed below the channel insulator, extending across the source; an insulating body for serving as a base to support the gate and the channel insulator; an insulating walls which stand over the source, forming a closed vacuum channel; and a drain formed over the vacuum channel. In both types, proper bias voltages are applied among the gate, the source and the drain to enable electrons to be field emitted from the source through the vacuum channel to the drain.