Liquid crystal display device and method of manufacturing the same

• US 4,948,231 A
• Filed: 01/18/1989
• Issued: 08/14/1990
• Est. Priority Date: 04/09/1984
• Status: Expired due to Fees

• Current Assignee: Hosiden And Philips Display Corporation (Koninklijke Philips N.V.)
• Original Assignee: Hosiden Electronics Co. Ltd. (Hosiden Corporation)
• Inventors: Miyake, Katsumi, Ugai, Yasuhiro, Okamoto, Kotaro, Aoki, Shigeo
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/300,688
• Time in Patent Office: 573 Days
• Field of Search: 350/334, 350/339 F, 350/332, 350/333, 357/23.7, 357/30 L
• US Class Current: 349/44
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 29/78 with field effect produced by an insulated gate H01L29/7725, H01L29/775, H01L29/778 take precedence

Abstract

A liquid crystal display device comprises a plurality of display electrodes which are selectively energized through on-off control of thin film transistors. In order to reduce the channel length of the thin film transistors to increase operation speed and obtain uniform characteristics, each display electrode and an associated transistor source electrode is formed on one of a pair of transparent substrates of the liquid crystal display device, a semiconductor layer is formed between the display layer and source electrode, a gate insulating film is formed on the semiconductor electrode, and a gate electrode is formed on a portion of the gate insulating film between the display electrode and source electrode. Then, ions are implanted into the semiconductor layer with the gate electrode used as a mask, thus rendering portions of the semiconductor layer contiguous to the display electrode and source electrode into ohmic layers. A channel is thus obtained between the ohmic layers with its length determined by the length of the gate electrode.

Claims

1. A liquid crystal display device comprising first and second transparent substrates closely spaced apart and facing each other, a liquid crystal sealed between said transparent substrates, a plurality of display electrodes made of ITO arranged in rows and columns on the inner surface of said first transparent substrate, thin film transistors formed on said first transparent substrate and each having a drain connected to one of said display electrodes, first source buses formed of the same material as said display electrodes and extending along corresponding columns of said display electrodes, each said source bus having source electrodes of said thin film transistors integrally formed therewith adjacent corresponding ones of said display electrodes, an opaque metal layer formed on said first transparent substrate and under each said thin film transistor, an insulating layer formed between each said metal layer and said thin film transistor, second source buses of the same material as said opaque metal layers formed integrally therewith to extend under said insulating layer along respective ones of said first source buses and connected thereto through holes formed in said insulating layer, and a transparent common electrode formed on and substantially over the entire inner surface of said second transparent substrate, said thin film transistors being selectively controlled for switching to apply a voltage between selected display electrodes and said common electrode for display,

said thin film transistors each including a semiconductor layer which extends between the corresponding display electrode and the source electrode, opposite marginal edges of said semiconductor layer partly overlying said display electrode and said source electrode on the side thereof opposite said first transparent substrate, a gate insulating film formed on said semiconductor layer entirely on the side thereof opposite said first transparent substrate, and a gate electrode formed on said gate insulating film,

each of said thin film transistors including a pair of gaps which are defined respectively between the opposite ends of said gate electrode and said display electrode and the source electrode when viewed in a direction perpendicular to said first transparent substrate, the width of each of said gaps being less than the thickness of said semiconductor layer, portions of said semiconductor layer overlying said display electrode and source electrode being ohmic layers having implanted ions of a concentration higher than an impurity concentration of a channel region of said semiconductor layer under said gate electrode, said channel region having the same length as the width of said gate electrode.

2. The liquid crystal display device according to claim 1, wherein light-blocking layers of an opaque metal are formed on portions of said second transparent substrate corresponding to gaps between adjacent display electrodes.

3. The liquid crystal display device according to claim 2, wherein color filters are formed on said second transparent substrate such that they face said display electrodes.

4. The liquid crystal display device according to claim 3, wherein said light-blocking layers are formed between said common electrode and said second transparent substrate.

5. The liquid crystal display device according to claim 4, wherein said light-blocking layers partly overlie said color filters on the side thereof opposite said second transparent substrate.

6. The liquid crystal display device according to claim 3 wherein said display electrodes are picture element electrodes arranged in a matrix array, said thin film transistors connected to the picture element electrodes in each column have their source electrodes connected to a corresponding one of said first source buses, said thin film transistors connected to the picture element electrodes in each row of said matrix array have their gate electrodes connected to a corresponding one of a plurality of gate buses, and said color filters consist of a plurality of different color filters which are substantially uniformly distributed.

7. The liquid crystal display device according to claim 1 wherein said display electrodes are picture element electrodes arranged in a matrix array, said thin film transistors connected to the picture element electrodes in each column have their source electrodes connected to a corresponding one of said first source buses, and said thin film transistors connected to the picture element electrodes in each row of said matrix array have their gate electrodes connected to a corresponding one of a plurality of gate buses.