A cathode device comprising a plurality of emitter tips having conical tip end portions to emit electrons therefrom. A gate electrode layer has an opening through which the tip end portion of each of the emitter tips is exposed. The diameter of the opening in the gate electrode layer is made smaller than that of the portion of the emitter tip at the juncture thereof with the substrate. In the fabrication of the cathode device, an oxide layer is formed at least on the surface of the formed emitter tip to sharpen the latter. By removing the oxide layer, an inner circumferential wall of the opening of the gate electrode layer is formed on the outside of the conical tip end portion of the emitter tip and extends approximately in parallel to the conical tip end portion of the emitter tip.