# US 2018/0026103 A1 · Transistor, thin-film transistor substrate, and liquid crystal display

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- Number: US 2018/0026103 A1
- Document ID: US20180026103A1
- Status: Published application
- Kind: A1
- Application number: 15/549,834
- Filed: 2016-04-14
- Published: 2018-01-25
- Earliest claimed: 2015-04-28
- Assignees: Mitsubishi Electric Corporation
- Applicants: Mitsubishi Electric Corporation
- Inventors: Rii HIRANO; Yusuke YAMAGATA; Naoki NAKAGAWA
- Web page: https://patentgrep.com/patent/US20180026103A1

## CPC

- H10D 62/86: being Group II-VI materials, e.g. ZnO
- G02F 1/1368: in which the switching element is a three-electrode device {(G02F1/136277 takes precedence)}
- H10D 30/6729: {characterised by the electrodes}
- H10D 30/6734: {having gate electrodes arranged on both top and bottom sides of the channel, e.g. dual-gate TFTs}
- H10D 30/675: {Group III-V materials, Group II-VI materials, Group IV-VI materials, selenium or tellurium}
- H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate}
- H10D 86/423: {comprising semiconductor materials not belonging to the Group IV, e.g. InGaZnO}
- H10D 86/60: wherein the TFTs are in active matrices
- H10K 59/1213: {the pixel elements being TFTs}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

The present technique relates to a transistor that uses an oxide semiconductor as its channel layer and that is capable of suppressing fluctuations in threshold voltage, and to a thin-film transistor substrate and a liquid crystal display that include such a transistor. The transistor is configured such that an overlap length, which is a length of overlap in plan view between the source electrode and the channel protective film in a direction from the source electrode toward the drain electrode, is longer than an overlap length, which is a length of overlap in plan view between the drain electrode and the channel protective film in a direction from the drain electrode toward the source electrode.

## Claims

### Claim at position 1

1: A transistor comprising:
a gate electrode;
a gate insulating film that covers at least said gate electrode;
an oxide semiconductor layer formed in a position on said gate insulating film, the position including a position that overlaps with said gate electrode in plan view;
a channel protective film that covers part of said oxide semiconductor layer;
a source electrode that covers part of said channel protective film and part of said oxide semiconductor layer; and
a drain electrode that is spaced from said source electrode and covers part of said channel protective film and part of said oxide semiconductor layer,
wherein a length of overlap in plan view between said source electrode and said channel protective film in a direction from said source electrode toward said drain electrode is longer than a length of overlap in plan view between said drain electrode and said channel protective film in a direction from said drain electrode toward said source electrode.

### Claim at position 2 (depends on 1)

2: The transistor according to claim 1, wherein
said oxide semiconductor layer is formed on the inner side of said gate electrode in plan view

### Claim at position 3 (depends on 1)

3: The transistor according to claim 1, operating in a depletion mode in which a threshold voltage is negative.

### Claim at position 4 (depends on 1)

4: A thin-film transistor substrate that is a thin-film transistor substrate including the transistor according to claim 1, wherein
said transistor is used in a circuit that drives a pixel transistor that is a transistor corresponding to a pixel in a liquid crystal display,
said circuit that drives the pixel transistor includes a first transistor, a second transistor, a third transistor, and a capacitor,
said first transistor has a source electrode connected to one electrode of said capacitor and to a drain electrode of said second transistor,
said capacitor has the other electrode connected to a gate electrode of said first transistor and to a source electrode of the third transistor,
at least said third transistor is the transistor according to claim 1, and
said transistor is formed on a substrate that is the same as said thin-film transistor substrate that is an array substrate on which said pixel transistor is formed.

### Claim at position 5 (depends on 1)

5: A thin-film transistor substrate that is a thin-film transistor substrate including the transistor according to claim 1, wherein
said transistor is used in an inverter circuit that drives a pixel transistor that is a transistor corresponding to a pixel in a liquid crystal display,
said inverter circuit that drives the pixel transistor includes a first transistor and a second transistor,
said first transistor has a source electrode connected to a gate electrode of said first transistor and to a drain electrode of said second transistor,
said second transistor has a source electrode connected to a power supply potential VSS,
at least said first transistor is the transistor according to claim 1, and
said transistor is formed on a substrate that is the same as said thin-film transistor substrate that is an array substrate on which said pixel transistor is formed.

### Claim at position 6 (depends on 1)

6: A thin-film transistor substrate that is a thin-film transistor substrate including the transistor according to claim 1, wherein
said transistor further comprises:
an additional protective film formed to cover said source electrode, said drain electrode, said channel protective film, and said gate insulating film; and
a top gate electrode formed in a position on an upper surface of said additional protective film, the position overlapping with said oxide semiconductor layer in plan view,
said transistor is used in a circuit that drives a pixel transistor that is a transistor corresponding to a pixel in a liquid crystal display,
said circuit that drives the pixel transistor includes a first transistor, a second transistor, a third transistor, and a capacitor,
said first transistor has a source electrode connected to one electrode of said capacitor and to a drain electrode of said second transistor,
said capacitor has the other electrode connected to a gate electrode of said first transistor and to a source electrode of the third transistor,
at least said first transistor is the transistor according to claim 1,
said top gate electrode of said first transistor is connected to said gate electrode of said first transistor, and
said transistor is formed on a substrate that is the same as said thin-film transistor substrate that is an array substrate on which said pixel transistor is formed.

### Claim at position 7 (depends on 1)

7: A thin-film transistor substrate that is a thin-film transistor substrate including the transistor according to claim 1, wherein
said transistor is used as a pixel transistor that is a transistor corresponding to a pixel in a liquid crystal display, and
said thin-film transistor substrate is an array substrate on which said pixel transistor is formed.

### Claim at position 8 (depends on 1)

8: A thin-film transistor substrate that is a thin-film transistor substrate including a plurality of transistors each being the transistor according to claim 1, wherein
said plurality of transistors include a transistor that is used to drive a pixel transistor that is a transistor corresponding to a pixel in a liquid crystal display, and a transistor that is used as said pixel transistor,
said thin-film transistor substrate is an array substrate on which said pixel transistor is formed, and
said transistor that is used to drive said pixel transistor is formed on a substrate that is the same as said thin-film transistor substrate.

### Claim at position 9 (depends on 4)

9: A liquid crystal display comprising:
the thin-film transistor substrate according to claim 4;
an opposite substrate disposed opposite said thin-film transistor substrate;
a liquid crystal layer that is sandwiched between said thin-film transistor substrate and said opposite substrate; and
a backlight disposed on a side of said thin-film transistor substrate opposite said opposite substrate.