LCD device having coupling capacitances and shielding films

• US 5,966,193 A
• Filed: 07/11/1997
• Issued: 10/12/1999
• Est. Priority Date: 07/15/1996
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Zhang, Hongyong, Miyamoto, Tadayoshi, Yoshinouchi, Atsushi, Takenouchi, Akira
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/891,697
• Time in Patent Office: 823 Days
• Field of Search: 349/110, 349/111, 349/38, 349/39
• US Class Current: 349/110
• CPC Class Codes: G02F 1/136209 Light shielding layers, e.g. black matrix, incorporated in the active matrix substrate, e.g. structurally associated with the switching element
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors

Abstract

This invention is characterized by providing light shield patterning on a TFT substrate for an active matrix type liquid crystal display device. A liquid crystal display device comprising an active matrix circuit using a TFT having a top gate-type structure. The light-shield film are formed under a semiconductor layer and superposed at least one of the source bus line and the gate bus line. A capacitance is formed by the light-shield film and at least a part of the semiconductor layer with an insulating layer interposed therebetween.

Claims

1. A liquid crystal display device having an active matrix circuit, said active matrix comprising:

a top gate-type TFT comprising a semiconductor film;

a pixel electrode being electrically connected at least a portion of said semiconductor film;

a first light shield film having a fixed electric potential formed under said semiconductor film;

at least one of a source bus line and a gate bus line shielded by said light shield film from light;

a first capacitance formed between the light shield film and said portion of the semiconductor film having an insulating film interposed therebetween; and

a second light shield film being formed over said TFT, a part of the second light shield film being overlapped with the first light shield film.

2. A device according to claim 1 further comprising another gate bus line,

wherein a second capacitance is formed between said semiconductor film and said another gate bus line.

3. A device according to claim 1 wherein the first light shield film is wider than at least one of the source bus line and the gate bus line.

4. A device according to claim 1 wherein said semiconductor film extends along said one of the source bus line and the gate bus line.

5. A device according to claim 1 wherein said first capacitance is formed between said light shield film and drain region in said semiconductor film of the TFT.

6. A semiconductor device comprising:

a first light shield film formed on a substrate;

a semiconductor film formed over said light shield film having a first insulating film therebetween, said semiconductor film including source and drain region and a channel region;

a first wiring formed over said channel region having a second insulating film therebetween; and

a second light shielding film formed over said first wiring interposed a third insulating film therebetween, a part of said second light shielding film being overlapped with said first light shielding film,

wherein a first capacitance is formed between said first light shield film and said semiconductor film.

7. A device according to claim 6 further comprising a second wiring shielded by said light shielding film,

wherein said semiconductor film extends along said second wiring.

8. A device according to claim 6 wherein said first capacitance is formed between said first light shielding film and said drain region in the semiconductor film.

9. A liquid crystal display device comprising:

a first light shield film formed on a substrate;

a semiconductor film formed over said first light shield film having a first insulating film therebetween, said semiconductor layer including source and drain region and a channel region;

a first wiring formed over said channel region having a second insulating film therebetween;

a second wiring formed over said source region having said second insulating film and a third insulating film therebetween, said second wiring being connected to said source region through a first opening;

an electrode formed over said drain region having said second insulating film and said third insulating film therebetween, said electrode being connected to said drain region through a second opening;

a second light shield film formed over said first wiring having said third insulating film and a fourth insulating film therebetween;

a leveling film covering said fourth insulating film and said second light shield film; and

a pixel electrode formed on said leveling film, said pixel electrode being connected to said electrode through a third opening,

wherein a first capacitance is formed between said first light shield film and said semiconductor film and a second capacitance is formed between said second light shield film and said pixel electrode.

10. A liquid crystal display device comprising:

at least a first gate line and a second gate line;

at least a source line;

a first light shielding film extending along and overlapping the source line, the first gate line, and the second gate line;

a thin film transistor comprising a semiconductor film, a gate insulating film, and a gate electrode, said thin film transistor being operationally connected to the source line and the first gate line while not being connected to the second gate line, wherein a first portion of said semiconductor film is located between the source line and the first light shielding film with insulating films interposed therebetween and a second portion of said semiconductor film is located between the second gate line and the first light shielding film with the insulating films therebetween;

a first capacitor formed between at least said first portion of the semiconductor film and the first light shielding film; and

a second capacitor formed between at least a second portion of the semiconductor film and the first light shielding film.