Method of manufacturing field emission device

A method of manufacturing of a field emission device comprising:

• forming a cathode layer on a substrate;
• forming a first insulating layer on the cathode layer;
• forming a gate electrode layer on the first insulating layer;
• forming a protection layer on the gate electrode layer;
• etching both of a portion of the protection layer and a portion of the gate electrode layer to form a first opening hole, a portion of the first insulating layer being exposed through the first opening hole;
• forming a second insulating layer on the protection layer and on the first opening hole, the second insulating layer filling the first opening hole;
• forming a focus electrode layer on the second insulating layer;
• forming a photoresist layer on the focus electrode layer;
• patterning both of a portion of the photoresist layer and a portion of the focus electrode layer to form a second opening hole where both of the portion of the photoresist layer and the portion of the focus electrode layer covering the first opening hole, a portion of the second insulating layer being exposed through the second opening hole;
• etching both of the portion of the second insulating layer and the portion of the first insulating layer to form an emitter hole, a portion of the cathode layer being exposed through the emitter hole;
• planarizing the emitter hole;
• removing the photoresist layer;
• and
• forming an electron emission emitter on the exposed portion of the cathode layer.

A field emission device comprising:

• a cathode layer formed on a substrate;
• a first insulating layer formed on the cathode layer;
• a gate electrode layer formed on the first insulating layer;
• a protection layer formed on the gate electrode layer;
• the stack of the protection layer, the gate electrode layer, and the first insulating layer having a plurality of first opening holes, portions of the cathode layer being exposed through the first opening holes;
• a second insulating layer formed on the protection layer;
• a focus electrode layer formed on the second insulating layer, the stack of the second insulating layer and the focus electrode layer having a second opening hole that is aligned with the first opening holes in a manner that the exposed portions of the cathode layer are also exposed through the second opening hole;
• and
• an electron emission emitter formed the exposed portion of the cathode layer.