An interesting article from the last online edition of AIP -- maybe vacuum tubes could make a comeback... What are the advantages of this type of transistor over a comparable non-vacuum one?
Vacuum nanoelectronics: Back to the future?—Gate insulated nanoscale vacuum channel transistor | Browse - Applied Physics Letters A gate-insulated vacuum channel transistor was fabricated using standard silicon semiconductor processing. Advantages of the vacuum tube and transistor are combined here by nanofabrication. A photoresist ashing technique enabled the nanogap separation of the emitter and the collector, thus allowing operation at less than 10 V. A cut-off frequency fT of 0.46 THz has been obtained. The nanoscale vacuum tubes can provide high frequency/power output while satisfying the metrics of lightness, cost, lifetime, and stability at harsh conditions, and the operation voltage can be decreased comparable to the modern semiconductor devices.