JP2001117115A - Active matrix type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a pixel finer or to enhance the opening ratio of the pixel by reducing the circuit area of a TFT(thin film transistor) in an active matrix type display device performing the switching of the pixel by using the TFT in which a double gate structure is employed. SOLUTION: The semiconductor film 12 of a TFT 3 has a double gate structure in which the film intersect one part of a gate line 2 twice and only a gate 15 remote from a data line 1 has a dual gate structure in which the semiconductor film 12 is held between the gate line 2 and a gate electrode 17 and a gate 14 has a single gate structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (Liquor display).
The present invention relates to a structure of a display device such as an id crystal display (LCD) or an organic EL display, and more particularly to a display device having an active matrix type using a thin film transistor (TFT) and having a TFT structure suitable for miniaturization.

[0002]

2. Description of the Related Art FIG. 4 is a plan view showing a conventional LCD as an example of a conventional active matrix display device. A plurality of data lines 51 extending in the vertical direction are arranged in parallel,
A plurality of gate lines 52 extending in a direction intersecting this are arranged in parallel. At each intersection of the data line 51 and the gate line 52, a TFT 53 and a pixel electrode 54 are arranged.

The TFT 53 has a semiconductor film 62 connected to the data line 51 via a contact 61, and is further connected to a pixel electrode 54 via a contact 63. The semiconductor film 62 intersects the gate line 52 at two points, and forms gates 64 and 65, respectively.

When a voltage is applied to the gate line 52, TF
A channel is formed in the semiconductor film 62 of T53 to be conductive, and the data voltage applied to the data line 51 is applied to the pixel electrode 5
4 and the liquid crystal is driven to perform display according to the data voltage.

[0005] In the present specification, a TFT having a plurality of gates as described above is referred to as a multiple gate, and a TFT structure having two gates is particularly referred to as a double gate. By making the TFT 53 a double gate, when the TFT is made non-conductive, a high resistance TFT is connected in series.
This has the effect of reducing an unintended leakage current that flows unintentionally during non-conduction, so-called off-leak current.

[0006] The TFT 53 further has a gate electrode 66. The gate electrode 66 is connected to the gate line 52 via a contact 67 and overlaps the gates 64 and 65.

FIG. 5 is a sectional view taken along the line AA 'in FIG. A gate line 52 is arranged on a glass substrate 71, and the first
The semiconductor film 62 of the TFT 53 via the gate insulating film 72 of FIG.
Is arranged. On the semiconductor film 62, the data line 51 and the gate electrode 66 are arranged in the same layer via a second gate insulating film 73. Further, a flattening film 74 and the like are formed,
A liquid crystal and a counter substrate (not shown) are arranged thereon.

In this specification, such a structure in which the semiconductor film 62 of the TFT 53 is sandwiched between the gate line 52 and the gate electrode 66 is called a dual gate. Gate electrode 66
Are connected to the gate line 52,
And the same potential. By making it a dual gate,
Since a channel is formed in the semiconductor film 62 by the electric field of each of the upper and lower gates, the resistance at the time of conduction is smaller than that of a TFT having no gate electrode 66, and the formation of a back channel can be suppressed. This has the effect of reducing the current.

In recent years, active matrix type display devices have been adopted as display devices for portable electronic devices, such as viewfinders of digital still cameras and digital video cameras. There is a demand for reducing the screen size and miniaturizing while maintaining the above.

[0010]

When the screen size is reduced while maintaining the number of pixels, the following problem occurs.

First, since the minimum line width that can be processed, that is, the so-called design rule, is constant, further miniaturization cannot be performed. That is, each structure formed in the same layer needs to have a minimum line width d based on the design rule and a minimum interval based on the design rule.
Further, when the line width of the wirings 51 and 52 and the area of the TFT 53, the contacts 61, 63 and 67, etc. are reduced, the electric resistance increases. Therefore, it is necessary to secure a certain line width and size.

Therefore, the screen size is reduced and the pixel electrodes 5
Even if 4 is designed to be small, there is a limit to the reduction of the wiring and TFT, and the area occupied by the TFT in the pixel is relatively increased. Was difficult. A switching element such as a TFT may malfunction when exposed to light. Therefore, it is necessary to dispose a light-shielding film. In a miniaturized display device, improvement of the aperture ratio has been a problem.

[0013] Further, even in a display device which is not miniaturized, there is a demand for reducing the area where the light-shielding film is formed and increasing the aperture ratio.

Accordingly, the present invention provides a double-gate TF with a smaller circuit area while maintaining constant TFT characteristics.
It is intended to provide a T structure.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a plurality of gate lines arranged in a row direction, a plurality of data lines arranged in a column direction, a gate line and a data line. A pixel electrode arranged in a matrix at each intersection point of the semiconductor and a semiconductor connected to the data line via the first contact, intersecting a part of the gate line, and connected to the pixel electrode via the second contact A first contact is provided on a side opposite to a pixel electrode with a gate line interposed therebetween, and the gate line is provided with a thin film transistor. The thin film transistor has a protruding portion that branches in a direction opposite to the pixel electrode controlled by the gate line. Data is a thin film transistor of the multi-gate structure having at least two gates.

The projection is formed so as to overlap a pixel electrode controlled by the thin film transistor and an adjacent pixel electrode adjacent to the pixel electrode interposed by the thin film transistor with a gate line intersecting the thin film transistor therebetween. It is arranged so as to overlap the pixel electrode.

Further, the thin film transistor further has a gate electrode electrically connected to the gate line, and a gate electrode disposed on the opposite side of the semiconductor film from the gate line or the protruding portion. It overlaps with a gate that is arranged so as to overlap with an adjacent pixel electrode.

[0018]

FIG. 1 is a plan view showing a first embodiment of the present invention. A plurality of data lines 1 extending in the vertical direction are arranged in parallel, and a plurality of gate lines 2 extending in a direction crossing the data lines 1 are arranged in parallel. A TFT 3 and a pixel electrode 4 are arranged at each intersection of the data line 1 and the gate line 2.

The TFT 3 has a semiconductor film 12 connected to the data line 1 via a contact 11, and the semiconductor film 12 is connected to a pixel electrode 4 via a contact 13. The semiconductor film 12 crosses the gate line 2 at two places,
The double gate structure has a gate 14 and a gate 15, respectively.

In this embodiment, the gate line 2 has a projection 2 '. The protruding portion 2 ′ overlaps the pixel electrode 4 ′ adjacent to the pixel electrode 4 via the gate line 2. The semiconductor film 12 intersects the protrusion 2 'on the adjacent pixel 4' to form a gate 14.

The TFT 3 further has a gate electrode 17 connected to the gate line 2 via a contact 16. The gate electrode 17 overlaps the gates 14 and 15 to form a dual gate structure. Therefore, since the gate electrode 17 exists between the semiconductor film 12 and the pixel electrode 4 ′, the influence of the electric field formed by the pixel electrode 4 ′ is blocked by the gate electrode 17, and the malfunction of the TFT 3 can be prevented. .

FIG. 2 is a sectional view taken along the line AA 'in FIG. The gate line 2 is arranged on a glass substrate 31, and the semiconductor film 12 of the TFT 3 is arranged via a first gate insulating film 32. On the semiconductor film 12, the data line 1 and the gate electrode 17 are arranged in the same layer via a second gate insulating film 33. Further, a flattening film 34 and the like are formed, and a liquid crystal and a counter substrate (not shown) are arranged thereon. Here, since the gates 14 are arranged so as to overlap on the adjacent pixels, the data line 1 and the gate electrode 17 formed in the same layer have an interval according to the design rule.

As described above, since the data line 1 and the gate electrode 17 are formed of the same layer, they need to be insulated, and it is necessary to secure a predetermined interval according to design rules. As is apparent from comparison with the shape of the conventional gate electrode 66 shown in FIG.
Since 4 overlaps with the adjacent pixel, the length of the gate electrode 17 in the row direction is reduced to about ／ as compared with the case where the gate 14 is arranged on the gate line 2. As a result, the TFT 3 can secure an interval according to the design rule while using both the double gate structure and the dual gate structure.

In this embodiment, the advantage of overlapping the gate 14 with the pixel electrode 4 will be described. The pixel electrode 4 and the protruding portion 2 ′ of the gate line 2 are formed so as to overlap with each other, and the gate line is a metal and serves as a light shielding region. Further, since the semiconductor film 12 is a transmissive film such as a polysilicon film, light is transmitted through an overlapping region between the pixel electrode 4 and the semiconductor film 12. By forming the protruding portion 2 ′ so as to overlap the pixel electrode 4, it can be used as a region that transmits light up to a region just below the protruding portion 2 ′, so that the aperture ratio is improved.

Further, the advantage of overlapping the gate 14 with the adjacent pixel electrode 4 will be described. Generally, a parasitic capacitance is generated between two opposing electrodes. Here, when the gate 14 is disposed so as to overlap the own pixel electrode 4, a parasitic capacitance occurs between the protrusion 2 and the pixel electrode 4, that is, a parasitic capacitance between the gate line 2 and the pixel electrode 4. Increase. When the parasitic capacitance between the gate line 2 and the pixel electrode 4 increases, there is a possibility that a malfunction may occur in the operation such as a change in the voltage of the pixel electrode due to the application of the gate voltage, and the parasitic capacitance needs to be minimized. On the other hand, the adjacent pixel electrode 4
When the gate 14 is formed so as to overlap with the adjacent pixel electrode 4
Is applied, the gate 14 itself is off,
There is an effect that not only there is no danger of operation failure, but also that it works as an auxiliary capacitance electrode.

The contact 11 between the semiconductor film 12 and the data line 1 is disposed on the opposite side of the pixel electrode 4 with the gate line 2 therebetween. Thereby, the semiconductor film 12
Unlike the semiconductor film 62 of the conventional TFT 53, the gate line 2 does not need to be formed back and forth, and only needs to intersect the gate line 2 once. Therefore, the length of the semiconductor film 12 can be reduced. Therefore, the semiconductor film 12 of the present embodiment has the protrusion 2 ′.
A double gate structure can be realized by bending once (L-shaped shape) together with the overlapping portion of Thereby, the area required for the semiconductor film 12 is greatly reduced. This is particularly important in reducing the screen size.

Next, FIG. 3 shows a plan view of an LCD according to a second embodiment of the present invention. The present embodiment is a so-called delta arrangement in which pixel electrodes adjacent in the column direction are shifted from each other by １ ／ pixel in the row direction. A plurality of data lines 1 'bent in the vertical direction are arranged, and a plurality of gate lines 2 are arranged in a direction intersecting the data lines 1'. At each intersection of the data line 1 and the gate line 2, a pixel electrode 4 is arranged via a TFT3. The description of the same configuration as that of the first embodiment is omitted.

In the delta arrangement, the data line 1 'is bent to shift the pixel electrode 4. In the present embodiment, as in the first embodiment, the gate 14 is formed so as to overlap the adjacent pixel electrode 4 ', thereby providing a double gate structure and a dual gate structure in accordance with the design rules. And could be adopted.

Although the above embodiment has been described by taking an LCD as an example, an active matrix type display device that performs switching by using a double-gate TFT may use, for example, an organic EL display or a fluorescent display tube. The present invention can be applied to any type of display device such as a fluorescent display device.

[0030]

As described above, according to the present invention,
First, since the first contact of the thin film transistor is provided on the opposite side of the pixel electrode with the gate line interposed therebetween, the semiconductor film of the thin film transistor only needs to intersect the gate line once, so that the area of the semiconductor film is reduced. Accordingly, a thin film transistor can be miniaturized.

Next, the gate line has a projection which branches in the direction opposite to the pixel electrode controlled by the gate line. Since the semiconductor film of the thin film transistor intersects with the gate projection, the thin film transistor After miniaturization, a thin film transistor having a multi-gate structure can be obtained.

Next, the projecting portion is formed so as to overlap a pixel electrode controlled by the thin film transistor and an adjacent pixel electrode adjacent to the thin film transistor with a gate line intersecting the thin film transistor interposed therebetween. Since the thin film transistor is arranged so as to overlap with the adjacent pixel electrode, the thin film transistor can be arranged without reducing the size of the pixel electrode, and a region through which light can be transmitted to just before the protrusion of the gate line can be formed. Rate can be improved.

Next, the thin film transistor further has a gate electrode electrically connected to the gate line, the gate electrode being disposed on the opposite side of the semiconductor film from the gate line or the projecting portion,
Since the gate electrode overlaps at least the gate arranged so as to overlap the adjacent pixel electrode of the thin film transistor,
The thin film transistor does not malfunction due to an electric field generated by an adjacent pixel.

By the way, in a large display device in which one pixel is large, the ratio of the area occupied by the TFT to one pixel is lower than that in a small display device. Therefore, the present invention is applied to a small display device such as a 4-inch type or less, for example, a 2-inch or 1.5-inch type, or a 4-inch or 6-inch type display device that displays high definition such as XGA. It is most effective.

[Brief description of the drawings]

FIG. 1 is a plan view of a display device according to a first embodiment.

FIG. 2 is a cross-sectional view of the display device according to the first embodiment.

FIG. 3 is a plan view of a display device according to a second embodiment.

FIG. 4 is a plan view of a conventional display device.

FIG. 5 is a cross-sectional view of a conventional display device.

[Explanation of symbols]

1 data line, 2 gate line,
3 TFT, 4 pixel electrode,
11, 13, 16 contacts 12 semiconductor films,
14 Single structure gate, 15 Dual gate structure gate, 17 Gate electrode

Claims (3)

[Claims] A plurality of gate lines arranged in a row direction, a plurality of data lines arranged in a column direction, pixel electrodes arranged in a matrix at respective intersections of the gate lines and the data lines, and A thin film transistor having a semiconductor film connected to a line via a first contact, intersecting a part of the gate line, and connected to the pixel electrode via a second contact. In the active matrix display device that switches the pixel electrode by using the first contact,
The gate line is provided on a side opposite to the pixel electrode with the gate line interposed therebetween, and the gate line has a protruding portion that branches in a direction opposite to a pixel electrode controlled by the gate line. An active matrix display device, wherein the thin film transistor has at least two gates, intersecting with the protrusion of the gate. 2. The protruding portion is formed so as to overlap a pixel electrode controlled by the thin film transistor and an adjacent pixel electrode adjacent to the pixel electrode that is interposed with a gate line intersecting the thin film transistor. 2. The display device according to claim 1, wherein the display device is disposed so as to overlap with the adjacent pixel electrode.
An active matrix display device according to item 1. 3. The thin film transistor further includes a gate electrode electrically connected to the gate line, the gate electrode being disposed on the opposite side of the semiconductor film from the gate line or the protrusion. 3. The active matrix display device according to claim 2, wherein at least a portion of the thin film transistor overlaps with a gate of the thin film transistor that overlaps with the adjacent pixel electrode.