A one-step electron-beam lithography process for fabrication of submicron air bridges is described. The fabrication principle is based on differing sensitivities of three layers of resist. By modulating the exposure dose it is possible to develop through all layers, the top layers only, or the center layer only (tunnels). We have fabricated the gate structure for making a quantum ring of 1 mu m diameter on GaAs material, with five separate Ti/Au Schottky gates around and in the center of the ring, including an air-bridge connection to the center gate.