JPH0519689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film transistor in a substrate for an active matrix liquid crystal display device.

[Summary of the invention]

In a substrate for an active matrix display device having a charge retention capacitor on a transparent insulating substrate, a charge retention capacitor portion is formed from a part of a pixel electrode consisting of a previous gate electrode, a gate insulating film, a semiconductor film, and a transparent electrode, By forming the semiconductor film in an island-like region separated from the transistor section and the drain wiring section, a substrate for an active matrix display device having good image quality can be provided.

[Conventional technology]

FIG. 2 shows an example of a unit pixel of a conventional active matrix liquid crystal display device. FIG. 2a shows a plan view of an example of a unit pixel structure, and FIG. 2b shows a plan view of an example of a unit pixel structure.
A cross-sectional view taken along line c-c' of Figure 2c is Figure 2a
FIG. 2 is a sectional view taken along line DD' of On the transparent insulating substrate 1 made of glass or _the like, cr , A _v , /C _r , M _p , A _l
A gate electrode 2 is provided, extending as a row electrode. The preceding gate electrode 2' is also illustrated. On the gate electrode 2, a gate insulating film 3 made of silicon dioxide, silicon dioxide, etc., and a semiconductor film 5 made of amorphous silicon, etc. are provided, and on the semiconductor film 5, a drain electrode 6 and a source electrode 7 as column electrodes are provided. The source electrode 7 and the pixel electrode 4 are connected to each other. A charge retention capacitor for retaining image signals and the like is composed of a front-stage gate electrode 2', a gate insulating film 3, a semiconductor film 5, and a pixel electrode 4. Note that the semiconductor film 5 of the transistor section and the charge holding capacitor section are arranged in a connected type. Furthermore, a light shielding film, a passivation film, etc. for blocking light from above may be formed, but these are not directly related to the present invention and will therefore be omitted. The structural examples shown in FIGS. 2a, b, and c have the drawback that image signals and the like written in the charge holding capacitor leak, making it impossible to obtain good image quality.

[Problem that the invention seeks to solve]

As shown in FIGS. 2a, b, and c, in the conventional structure, the image signal written in the charge holding capacitor leaks to the drain electrode 6 or source electrode 7' via the semiconductor film 5. Image signals are not maintained and image quality with good contrast cannot be obtained. The present invention solves the above problems and provides a unit pixel structure of thin film transistors for an active matrix display device that has good image quality without particularly increasing the number of man-hours.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention prevents leakage of image signals and the like by separately forming the semiconductor film formed in the charge holding capacitor part and the transistor part.

[Effect]

With the above configuration, for example, the image signal written in the charge holding capacitor is held without leaking through the semiconductor film, and image quality with good contrast can be achieved without increasing the number of steps.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings. FIG. 1a shows a plan view of a structural example of a unit pixel according to the present invention. Figure 1b is A- in Figure 1a.
A cross-sectional view along line A', Figure 1c is B of Figure 1a.
FIG. 3 is a cross-sectional view taken along line -B'. Gate electrodes 2 such as _Al , _cr , and _Mp are provided on a transparent insulating substrate 1 made of glass or the like and extend as row electrodes. The preceding gate electrode 2' is also shown. Gate electrode 2
A gate insulating film 3 made of silicon dioxide, silicon nitride, etc., and a semiconductor film 5 made of amorphous silicon, etc. are formed thereon. , an insulating film 3' and a semiconductor film 5', which are laminated simultaneously with the gate insulating film 3 and semiconductor film 5, are formed on the previous gate electrode 2',
A charge retention capacitor is constituted by a part of the pixel electrode 4 which is a transparent conductive film such as ITO. A drain electrode 6 and a source electrode 7 as column electrodes are arranged on the semiconductor film 5, and the source electrode 7 and the pixel electrode 4
is connected. By forming the semiconductor film 5' of the charge retention capacitor part in an island-like region separated from the semiconductor film 5 on which the drain electrode 6 and source electrodes 7 and 7' are arranged, it is possible to Since the semiconductor film 5' is formed in an island shape, the image signal is held without leakage, and an image display with good contrast can be obtained without increasing the number of steps. Although it is possible to configure the charge retention capacitor by eliminating the semiconductor film 5', this may cause damage to the insulating film 3' due to etchant etc. during patterning of the semiconductor film 5 of the transistor section, causing breakdown voltage failure. Therefore, a structure in which the semiconductor film 5' is formed into an island shape as shown in the present invention is preferable.

〔Effect of the invention〕

As explained above, the present invention provides an active matrix that has good image quality without increasing the number of manufacturing steps for a substrate for an active matrix display device in which unit pixels are arranged in a matrix, and without impairing the withstand voltage of the charge retention capacitor. A thin film transistor in a substrate for a liquid crystal display device can be provided.

[Brief explanation of the drawing]

FIG. 1a is a plan view of an example of a unit pixel structure of a thin film transistor according to the present invention, FIG. 1b is a cross-sectional view taken along line A-A' in FIG. 1a, and FIG.
FIG. 3 is a sectional view taken along line BB' in FIG. FIG. 2a is a plan view of an example of a conventional unit pixel structure.
Figure b is a cross-sectional view taken along line c-c in Figure 2 a;
Figure c is a sectional view taken along line D-D' in Figure 2a. 1... Substrate, 2, 2'... Gate electrode, 3...
Gate insulating film, 4...pixel electrode, 5, 5'... semiconductor film, 6... drain electrode, 7... source electrode.

Claims (1)

[Claims] 1. In a substrate for an active matrix display device in which at least a charge retention capacitor section is constituted by a preceding gate electrode, a gate insulating film, a semiconductor film, and a part of a pixel electrode made of a transparent conductive film, the semiconductor film is 1. A substrate for an active matrix display device, characterized in that the substrate is formed in an island-like region separated from at least a transistor section and a drain wiring section.