Transverse electrical field LCD with islands having a pattern the same as the combined pattern of gate electrodes, gate bus lines and counter electrodes

• US 5,990,987 A
• Filed: 11/17/1998
• Issued: 11/23/1999
• Est. Priority Date: 11/18/1997
• Status: Expired due to Term

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NEC Corporation
• Inventors: Tanaka, Hiroaki
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Eisenhut, Heidi L.
• Application Number:
  US09/192,535
• Time in Patent Office: 371 Days
• Field of Search: 349/139, 349/141, 349/143, 349/42, 349/43
• US Class Current: 349/43
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

In a production process for a transverse electrical field type active matrix liquid crystal display apparatus, a photolithographic step is eliminated to reduce the cost. There are formed on an insulating substrate carrying thin-film transistors as switching elements, drain electrodes 31, drain bus lines 32 connected to the drain electrodes 31, source electrodes 33 and pixel electrodes 34 formed by the first low-resistance electrically conductive film 3. Islands are formed on the resulting assembly by a semiconductor film. There are further formed on the resulting product gate electrodes 61, gate bus lines 62 and counter electrodes 63. The gate electrodes 61, gate bus lines 62, counter electrodes 63 and the islands 71 can be formed by a sole photolithographic step to reduce the number of the photographic steps and hence the cost.

Claims

1. A transverse electrical field type active matrix liquid crystal display apparatus having thin film transistors as switching elements,

in which there are disposed, on an insulating substrate carrying said thin-film transistors, drain electrodes, drain bus lines connected to said drain electrodes, source electrodes and pixel electrodes connected to said source electrodes, each formed of a first low-resistance electrically conductive film, with islands of a semiconductor film being formed thereon, and

in which there are further disposed thereon gate electrodes, gate bus lines connected to said gate electrodes and counter electrodes in the shape of a comb having its teeth disposed meshing with said pixel electrodes, each being formed of a second low-resistance electrically conductive film with interposition of a transparent insulating film above said islands provided that the gate electrodes overlapping with at least part of the drain electrodes and the source electrodes,

wherein said islands form a pattern which is substantially the same as a combined pattern of the gate electrodes, the gate bus lines and the counter electrodes.

2. The liquid crystal display apparatus as defined in claim 1,

wherein a lower layer semiconductor film is selectively formed on the surfaces of said drain electrodes, drain bus lines, source electrodes, and pixel electrodes, which were formed by the first low-resistance electrically conductive film and

wherein the semiconductor film of said islands is formed on said lower layer semiconductor film.

3. A method for producing a transverse electrical field type active matrix liquid crystal display apparatus comprising the steps of:

forming a transparent insulating film and a first low-resistance electrically conductive film in this order on an insulating substrate;

patterning said first low-resistance electrically conductive film to form drain electrodes, drain bus lines connected to the drain electrodes, source electrodes and pixel electrodes connected to the source electrodes, respectively;

forming a semiconductor film, a transparent insulating film and a second low-resistance electrically conductive film in this order on said insulating substrate; and

patterning said second low-resistance electrically conductive film to form a first pattern of gate electrodes, gate bus lines connected to said gate electrodes and counter electrodes, and patterning the transparent insulating film and the semiconductor film to form islands having a second pattern substantially identical to the first pattern.

4. The method for producing a liquid crystal display apparatus as defined in claim 3 further comprising the step of:

forming a lower layer semiconductor film on the surfaces of said drain electrodes drain bus lines, source electrodes and pixel electrodes which were formed by the first low-resistance electrically conductive film,

wherein said semiconductor film forming said islands is formed on said lower layer semiconductor film.

5. The method for producing a liquid crystal display apparatus as defined in claim 3, wherein said patterning said second low-resistance electrically conductive film is carried out by etching based on a sole photolithographic step employing a single photoresist.