A field emission device comprises a glass substrate, an emitter electrode formed on the glass substrate, a carbon nanotube (CNT) emitter formed on the emitter electrode, and a gate stack formed around the CNT emitter for extracting electron beams from the CNT emitter and focusing the extracted electron beams onto a given position. The gate stack includes a mask layer covering the emitter electrode and provided around the CNT emitter, a gate insulating layer formed on the mask layer to a predetermined height, a mirror electrode formed on an inclined plane of the gate insulating layer, a gate electrode formed on the gate insulating layer and spaced apart from the mirror electrode, and a focus gate insulating layer and a focus gate electrode sequentially formed on the gate electrode. The field emission device is manufactured and employed in a display device in accordance with the present invention.