assume the form of a trench a metallic membrane 22 is then deposited over the photoresist 18 and exposed portions of the anode contact layers 16 to establish a plating base for the anode a second layer of photoresist 24 is next applied over the anode plating layer 22 and then exposed and developed so that the remaining portions of photoresist layer 24 are on the opposite sides of anode openings 20 from the emitter array as shown in fig1 c thus only those portions of membrane 22 which span the emitter array or line the anode openings 20 are exposed a metal anode layer 26 is then plated onto the exposed membrane 22 as illustrated in fig1 d the remaining portions of the upper photoresist layer 24 are now removed followed by etching away the exposed membrane layer 22 lateral to the anode 26 and finally by dissolving the lower photoresist layer 18 the resulting fet structure is shown in fig1 e it is supported on the substrate only at its opposite ends with the entire volume between it and the underlying substrate and cathode gate structure left open the metal anode 26 forms an air bridge over the field emitter and gate elements while its method of fabrication is similar to that employed in prior air bridges used for metallization crossovers its function is totally different whereas the purpose of the prior crossover air bridges is to electrically isolate the bridging metal from the underlying conductor the purpose of the present anode air bridge is to establish an electric field between the cathodes 2 and the air bridge such that an emission of electrons from the cathodes and a current flow between the cathodes and air.