A porous dielectric material such as silica-based aerogel is used as the dielectric layer 48 between the gate and the cathode on the emitter plate 12 of a field emission device. Aerogel, which can have a relative dielectric constant as low as 1.03, is deposited over the resistive layer 44 of the emitter plate 12. Metal layer 49, functioning as the gate electrode, is subsequently deposited over the aerogel layer 48. The use of aerogel as a gate dielectric reduces power consumption. In a disclosed embodiment, aerogel layer 48 is comprised of sublayers 48a, 48b, and 48c of aerogels of differing densities, thereby providing better adhesion of the aerogel gate dielectric to both the resistive layer 44 and metal layer 49. Methods of fabricating the aerogel gate dielectric are disclosed.