An array of 3×4 ultrashallowp+–n++silicon junctions with gate (grid) structure has been developed for application as a micro‐vacuum triode. The device is fabricated by low energy ion implantation in conjunction with a new anode oxidation technique. The final junction depth is estimated to be 150 Å. Device structure and fabrication processes, especially on the formation and monitoring of the ultrashallow junction, are described. The current emission characteristics of the triode are investigated as a function of anode voltage, gate (grid) voltage, anode–emitter distance, and reverse bias current. The typical emission efficiency measured on bare silicon is 7.6×10−5.