JP3207760B2 - Semiconductor device and image display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a thin film transistor formed on a transparent insulating substrate, and more particularly to a semiconductor device having a structure for preventing deterioration of characteristics due to light. The present invention also relates to an image display device using the semiconductor device.

[0002]

2. Description of the Related Art At present, an active matrix driving type liquid crystal display device is well known as one of the image display devices which are widely put into practical use. As shown in FIG. 10, this type of liquid crystal display device includes a pixel array 51, a scanning signal line driving circuit 52, and a data signal line driving circuit 53.

The pixel array 51 includes n × m scanning signal lines GLj (j = 1, j = 1,
2,..., N: However, when collectively referred to simply as GL) and the data signal line SLi (i = 1, 2,..., M:
SL is used to collectively refer to), two adjacent scanning signal lines GL and two adjacent data signal lines SL
· It is composed of n × m pixels 54 provided in a portion surrounded by SL. As described above, one scanning signal line GL is assigned to one row and one data signal line SL is assigned to one column in the pixels 54 arranged in a matrix. The scanning signal line GL is connected to a scanning signal line driving circuit 52, and the data signal line SL is connected to a data signal line driving circuit 53.

The scanning signal line driving circuit 52 uses the circuit synchronizing signals CKG and GPS and the start pulse SPG generated by the timing signal generating circuit 65 (see FIG. 11) and the like to connect the scanning signal lines GL in the pixel array 51 to each other. In response, a scanning signal is output. On the other hand, the data signal line driving circuit 53
Is calculated using a synchronization signal CKS and a start pulse SPS also generated by the timing signal generation circuit 65 and the like.
The input video signal DAT is transferred (or amplified and transferred) to the data signal line SL. Further, the scanning signal line driving circuit 52 and the data signal line driving circuit 53 include, for example,
It is driven by power supply voltages VGH and VGL and power supply voltages VSH and VSL generated by the internal power supply generation circuit 66 (see FIG. 11) and the like.

Conventionally, in many active matrix type liquid crystal display devices, a thin film transistor as an active element used in the above-described pixel 54 has been constituted by an amorphous silicon thin film transistor formed on a glass substrate. Further, the scanning signal line driving circuit 52 and the data signal line driving circuit 53 are a plurality of driver ICs externally mounted on a glass substrate.

On the other hand, in recent years, in order to reduce the size, improve the reliability and reduce the cost of the liquid crystal display device, FIG.
1, the scanning signal line driving circuit 52 and the data signal line driving circuit 53 are connected to the same insulating substrate 5 as the pixel array 51.
5 is being developed for monolithic construction.

In this case, as the thin film transistor used as an active element, a field effect transistor formed of a single crystal, polycrystalline or amorphous silicon thin film is used. In fact, it can be formed in a large area,
In addition, a polycrystalline silicon thin film transistor is often used because a high driving force required for the scanning signal line driving circuit 52 and the data signal line driving circuit 53 can be obtained.

A conventional polycrystalline silicon thin film transistor has, for example, a structure as shown in FIG. In this structure, a silicon oxide film 56 is deposited on an insulating substrate 55 for preventing contamination, and a field effect transistor 57 is formed thereon.

The field effect transistor 57 has a polycrystalline silicon thin film 58 comprising a channel region 58a, a source region 58b and a drain region 58c formed on a silicon oxide film 56, and a gate insulating film 59 formed thereon. , A gate electrode 60, a silicon oxide film 61 as an interlayer film, a source electrode 62 and a drain electrode 63.

By the way, in a transmission type liquid crystal display device or the like,
Although high-intensity light is irradiated, the polycrystalline silicon thin-film transistor described above has been observed to increase in leak current and shorten its life due to light irradiation. This characteristic deterioration occurs when light is applied to the channel region or the junction of the transistor, and can be prevented to some extent by shielding the channel region and the vicinity of the junction with light.

Conventionally, for such a purpose, in the semiconductor device shown in FIG. 12, a chromium film or chromium film is formed at a position not in contact with the channel region 58a on the side opposite to the gate electrode 60. A light-shielding material 64 made of a laminated film of chromium oxide or the like is laid. However, since these light-shielding materials 64 are conductive, they may function as the fourth electrode of the field-effect transistor 57. For example, when the light-blocking material 64 is kept in an electrically floating state for a long period of time, charge accumulation occurs, and an unintended voltage may be applied to the channel region 58a. That is, depending on the voltage applied to the channel region 58a by the light-shielding material 64, the conduction of the field-effect transistor 57 may be controlled.

In order to avoid such a situation, in the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 60-192370, a light-shielding material is connected to a preceding or subsequent gate line (scan signal line). Has been proposed. Thus, in most of the holding period, the off voltage of the scanning signal is applied to the light-shielding material, so that a normal display can be obtained without turning on the thin film transistor.

[0013]

However, in the above-described conventional configuration, when a polycrystalline silicon thin film transistor or the like is used as the field effect transistor 57, when a voltage of a reverse polarity (a large off-state voltage) is applied to the gate electrode, There is a phenomenon that the leak current increases. Also, in this case,
There is also a problem that the characteristics are greatly deteriorated and the reliability of the field effect transistor 57 is impaired. Further, applying the off-voltage of the scanning signal to the light-shielding material as in the above-described disclosed technique applies the off-voltage from both sides of the channel region 58a, and thus the off-current applied to the channel region 58a Becomes big. Therefore, a problem arises in that the leak current increases and the characteristics of the thin film transistor deteriorate.

Further, a new wiring is required to apply another voltage to the light-shielding material. In this case, the performance of the liquid crystal display device, particularly, the aperture ratio may be reduced by the added wiring.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to maintain the light-shielding property of a transistor without deteriorating the aperture ratio and to deteriorate the characteristics of the transistor. It is an object of the present invention to provide a semiconductor device capable of applying a unique optimal voltage to a light-shielding material, and to provide a highly reliable image display device capable of displaying a good image by using the semiconductor device.

[0016]

According to a first aspect of the present invention, there is provided a semiconductor device comprising a plurality of thin film transistors formed on a transparent insulating substrate. A conductive light-blocking film that blocks light irradiation to the channel region of the active layer, a transparent electrode that interconnects the light-blocking films, and a light-shielding film that is connected to the transparent electrode and stabilizes the potential of the light-blocking film. (E.g., ground or DC power supply).

According to the above arrangement, the light-shielding films are connected to each other by the transparent electrode, and are connected to the potential stabilizing means via the transparent electrode. Therefore, the electrons jumping into the light shielding film flow out to the potential stabilizing means through the transparent electrode. Therefore, no charge is accumulated in the light-shielding film, and there is no possibility that an unintended voltage is applied to the channel. Also, since the wiring for letting out the charge jumping into the light shielding film is made of a transparent electrode,
The aperture ratio does not decrease.

According to a second aspect of the present invention, in order to solve the above-mentioned problems, in addition to the first aspect, the potential stabilizing means comprises a power supply for applying a predetermined voltage to the light-shielding film. Features.

According to the above configuration, a predetermined voltage can be applied to the light shielding film by the potential stabilizing means connected to the transparent electrode. Here, if an optimal value is selected for the voltage applied to the light shielding film, the threshold value of the thin film transistor can be shifted to an optimal value. As a result, it is possible to minimize a decrease in the off characteristic (increase in leak current) and a decrease in reliability of the thin film transistor.

According to a third aspect of the present invention, in order to solve the above-mentioned problem, in addition to the configuration of the second aspect, the light-shielding film is provided at a position facing the gate electrode of the thin film transistor with respect to the channel region. It is characterized by being arranged.

According to the above configuration, since no gate electrode exists between the light-shielding film and the channel region, the electric field by the light-shielding film is not shielded by the gate electrode. Therefore, the potential of the channel region can be easily controlled by the potential of the light-shielding film, and the threshold value of the thin film transistor can be controlled.

According to a fourth aspect of the present invention, there is provided an image display device, wherein a plurality of display pixels are provided in a matrix on a transparent insulating substrate, and display is performed by individually driving these pixels. In order to solve the problem of the above, the pixel,
A thin film transistor as a switching element for switching the pixel, and a conductive light shielding film for shielding irradiation of light to a channel region of an active layer of the thin film transistor,
A transparent electrode connected to the light-shielding film and connected to a potential stabilizing means for stabilizing the potential of the light-shielding film.

With the above arrangement, the light-shielding film of the thin-film transistor used as the switching element of the pixel is connected to the transparent electrode and to the potential stabilizing means via the transparent electrode. Therefore, the electrons jumping into the light shielding film flow out to the potential stabilizing means through the transparent electrode. Therefore, no charge is accumulated in the light-shielding film, and there is no possibility that an unintended voltage is applied to the channel. Further, since the wiring for letting out the electric charge jumping into the light shielding film is made of a transparent electrode, the aperture ratio does not decrease. As a result, a liquid crystal display device having high reliability and excellent display quality can be provided.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problems, in addition to the configuration of the fourth aspect, the potential stabilizing means comprises a power supply for applying a predetermined voltage to the light shielding film. It is characterized by.

With the above configuration, a predetermined voltage can be applied to the light-shielding film of the thin film transistor used as a switching element of the pixel by the potential stabilizing means connected to the transparent electrode. Here, if an optimal value is selected for the voltage applied to the light shielding film, the threshold value of the thin film transistor can be shifted to an optimal value. As a result, it is possible to minimize a decrease in the off characteristic (increase in leak current) and a decrease in reliability of the thin film transistor. Therefore, the retention rate and long-term reliability of the pixel can be improved.

According to a sixth aspect of the present invention, in addition to the configuration of the fourth or fifth aspect, the light shielding film is disposed at a position facing the gate electrode of the thin film transistor with respect to the channel region. Features.

According to the above configuration, since no gate electrode exists between the light shielding film and the channel region of the thin film transistor, the electric field by the light shielding film is not shielded by the gate electrode. Therefore, the threshold value of the thin film transistor can be easily controlled, and the retention rate and long-term reliability of the pixel can be improved with low power.

According to a seventh aspect of the present invention, in addition to the configuration of any of the fourth to sixth aspects, the transparent electrode is provided on a pixel array composed of the respective pixels on an image forming surface of the pixel array. It is characterized by being laid all over.

According to the above configuration, the respective light-shielding films are connected to each other by the above-mentioned transparent electrodes laid over the entire image forming surface of the pixel array. Therefore,
If only one potential stabilizing means is provided, the potential can be stabilized for all the light shielding films. Further, since the transparent electrode is laid on the pixel array composed of the pixels over the entire image forming surface of the pixel array, the resistance of the transparent electrode (the light shielding film and the voltage supply terminal of the power supply unit) ), And a stable voltage can be applied to the light-shielding film.

According to an eighth aspect of the present invention, in addition to the configuration of the seventh aspect, the transparent electrode is divided into a plurality of parts on the pixel array, and the potential is applied to each of the divided transparent electrodes. It is characterized in that the stabilizing means is connected.

According to the above configuration, the transparent electrode is laid in a plurality of regions of the pixel array.
Then, in the divided regions, the light-shielding films are connected to each other by the transparent electrodes. Thus, even when the characteristics of the thin film transistors have a distribution (variation) in the pixel array, an optimal voltage can be applied to the light-shielding film in each region, and the display quality can be improved.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIGS.

First, the structure of the semiconductor device according to the present embodiment will be described with reference to FIG. Here, a semiconductor device used for a transmission type liquid crystal display device as an image display device will be exemplified.

As shown in FIG. 1, the semiconductor device has a structure having a plurality of thin film transistors 4 formed on a transparent insulating substrate 1. In the above semiconductor device, a transparent electrode layer (transparent electrode) 2 made of ITO (Indium Tin Oxide) or the like is laid on a transparent insulating substrate 1. On the transparent electrode layer 2, a light-shielding film 3 made of chromium, titanium, tantalum, or the like is in contact with the transparent electrode layer 2.
Are provided corresponding to the thin film transistors 4. As the transparent insulating substrate 1, a sapphire substrate,
A quartz substrate, non-alkali glass, or the like is often used.

The transparent electrode layer 2 is connected to a DC power supply 13 via a ground wiring 12. The ground wiring 12 and the DC power supply 13 constitute a potential stabilizing means for stabilizing the potential of the light shielding film 3. The DC power supply 13 has a plus side grounded and a minus side connected to the ground wiring 12. Thereby, the light shielding film 3 becomes
A negative voltage will be applied. In FIG. 1, as described above, a negative voltage is applied to the light shielding film 3. However, if desired, the direction of the DC power supply 13 is reversed and a positive voltage is applied to the light shielding film 3. Can also be applied.

The thin film transistor 4 is provided above the light shielding film 3 with a silicon oxide film 5 interposed therebetween. The thin film transistor 4 has a positive stagger structure formed of a polycrystalline silicon thin film. That is, the above-described thin film transistor 4 includes a polycrystalline silicon thin film 6 as an active layer including a channel region 6a, a source region 6b, and a drain region 6c formed on a silicon oxide film 5, and a gate insulating film formed thereon. 7,
It is formed by a gate electrode 8, an interlayer insulating film 9, a source electrode 10 and a drain electrode 11.

The gate electrode 8 is provided at a position facing the channel region 6a via the gate insulating film 7. The source electrode 10 is connected to the source region 6b via a contact hole 14 provided in the gate insulating film 7 and the interlayer insulating film 9. The drain electrode 11
Is connected to the drain region 6c via a contact hole 15 provided in the gate insulating film 7 and the interlayer insulating film 9.

Thus, the light-shielding film 3 is arranged below the thin-film transistor 4 so as to face the gate electrode 8 with the silicon oxide film 5 interposed therebetween. The light shielding film 3 allows the thin film transistor 4 to emit light from below.
That is, it has a light-shielding effect on light transmitted through the transparent insulating substrate 1.

Since the light-shielding film 3 has conductivity, it is insulated when a current flows through the thin-film transistor 4 or another wiring (a conductive layer forming the gate electrode 8, the source electrode 10, the drain electrode 11, etc.). Electrons may jump over the layer. The jumped-in electrons are emitted to the outside through the transparent electrode layer 2 and the ground wiring 12 connected to the transparent electrode layer 2. Therefore, no charge is accumulated in the light-shielding film 3, and the potential of the light-shielding film 3 is always kept constant. Therefore, the light shielding film 3 does not apply an unintended voltage to the thin film transistor 4.

Since a DC power supply 13 is connected to the ground wiring 12, the DC power supply 13
When an appropriate voltage is applied to each light-shielding film 3 via the transparent electrode layer 2, the threshold voltage of the thin film transistor 4 can be shifted to an optimum value, and the characteristics of the thin film transistor 4 can be improved. Therefore, characteristics of the thin film transistor can be improved in terms of operation speed, retention characteristics, and the like.

According to the above configuration, the wiring for supplying a bias to each light shielding film 3 from the outside is the transparent electrode layer 2 made of a transparent conductive material. Therefore, the light transmission efficiency does not decrease due to the wiring.

The transparent electrode layer 2 connects a plurality of light shielding films 3 to each other, and a constant voltage is applied from an external DC power supply 13. As a result, since a constant voltage is applied to the light-shielding film 3 via the transparent electrode layer 2, it is possible to apply an optimum bias to each light-shielding film 3 so as not to adversely affect the characteristics of the thin film transistor 4. it can.

In FIG. 1, each light shielding film 3 is formed so as to shield the entire thin film transistor 4 from light.
It is necessary only that the light-shielding film 3 shields the light from the area where the characteristic deterioration occurs due to the light irradiation, that is, only in the vicinity of the channel region 6a of the thin film transistor 4 and its junction. Therefore, as shown in FIG.
May be formed so as to shield only the channel region 6a and the vicinity of its junction.

In the present embodiment, the thin film transistor 4 having a normal staggered structure of polycrystalline silicon has been described as an example. However, the present invention is not limited to this, and other structures such as an inverted staggered structure, or amorphous silicon A thin film or a thin film using a compound semiconductor such as CdSe may be used.

However, when the structure of the thin film transistor 4 is an inverted staggered structure as shown in FIG. 3, the gate electrode 8 is on the lower side of the channel, and the light shielding film 3 is on the upper side. That is, in this case, the semiconductor device is applied to a liquid crystal display device having a system configuration in which a backlight is irradiated from above.

Further, in the present embodiment, the transparent electrode layer 2
Is grounded and connected to the DC power supply 13, but one of the ground and the DC power supply 13 may be omitted. For example, even when the ground is not taken, the electrons that have jumped into the light-shielding film 3 flow out to the DC power supply 13, so that the potential of the light-shielding film 3 is kept constant.

As described above, in this embodiment, the semiconductor device has been described. However, an image display device using the semiconductor device will be described in a second embodiment below.

(Embodiment 2) The following will describe another embodiment of the present invention with reference to FIGS. In this embodiment, a liquid crystal display device will be described as an image display device.

The liquid crystal display device according to the present embodiment has the structure shown in FIG.
As shown in FIG. 7, an active matrix driving type liquid crystal display device using the semiconductor device described in the first embodiment. The liquid crystal display device includes a pixel array 19, a scanning signal line driving circuit 34, and a data signal line driving circuit 30.

The pixel array 19 has nxm scanning signal lines GLj (j = 1,
2,..., N: However, when collectively referred to simply as GL) and the data signal line SLi (i = 1, 2,..., M:
SL is used to collectively refer to), two adjacent scanning signal lines GL and two adjacent data signal lines SL
· It is composed of n × m pixels 20 provided in a portion surrounded by SL. As described above, one scanning signal line GL is assigned to one row and one data signal line SL is assigned to one column in the pixels 20 arranged in a matrix. The scanning signal line GL is connected to the scanning signal line driving circuit 34, and the data signal line SL is connected to the data signal line driving circuit 30.

The data signal line driving circuit for transmitting a data signal to the data signal line SL includes a dot sequential driving method and a line sequential driving method. Here, in order to simplify the description, only the dot sequential driving method will be described.

As shown in FIG. 5, in the data signal line drive circuit 30 of the dot sequential drive system, the start pulse SPS input to the shift register 31 is sequentially shifted in synchronization with the synchronization signal CKS. As a result, the shift register 31
The output start pulse SPS is supplied to the sampling switch 33 via the buffer circuit 32. When the sampling switch 33 is closed by the pulse,
The video signal DAT is supplied to the data signal line SL through the sampling switch 33.

On the other hand, as shown in FIG.
In the scanning signal line driving circuit 34 for sending a scanning signal to the shift register 35, the start pulse SPG
Are sequentially shifted in synchronization with the synchronization signal CKG. As a result, the start pulse SPG output from the two adjacent shift registers 35 is supplied to the buffer circuit 36.
The sum is obtained in an AND circuit 37 via 36. Further, the sum of the output of the AND circuit 37 and the synchronizing signal GPS for determining the signal width of the scanning signal is obtained by the AND circuit 38, thereby generating a scanning signal. This scanning signal is applied to each scanning signal line GL via the buffer circuit 39.
In the scanning signal line driving circuit 34, the output amplitude of the scanning signal may be increased by using a buffer having a built-in level shifter.

Each signal applied to the data signal line driving circuit 30 and the scanning signal line driving circuit 34 is generated by a timing signal generating circuit (not shown). The data signal line driving circuit 30 and the scanning signal line driving circuit 34 are driven by power supply voltages VGH and VGL and power supply voltages VSH and VSL generated by an internal power supply generation circuit (not shown).

As shown in FIG. 7, each pixel 20 includes a thin film transistor 21 serving as a switching element and a liquid crystal capacitor 2.
2a.
Generally, a pixel capacitor 22 in an active matrix type liquid crystal display device has a liquid crystal capacitor 2 in order to stabilize display.
It has an auxiliary capacitor 22b added in parallel with 2a.
In other words, the auxiliary capacitance 22b has a leakage current of the liquid crystal capacitance 22a and the thin film transistor 21, a variation in pixel potential due to a parasitic capacitance such as a capacitance between a gate and a source and a capacitance between a pixel electrode and a signal line of the thin film transistor 21, and a display data dependence of the liquid crystal capacitance 22a. The influence of gender etc. is to be minimized.

The gate electrode of the thin film transistor 21 is connected to the scanning signal line GL. Also, the liquid crystal capacitor 22a
And one electrode of the auxiliary capacitor 22b is connected to the data signal line S via the drain and source of the thin film transistor 21.
L. The other electrode of the liquid crystal capacitor 22a is
The other electrode of the auxiliary capacitance 22b is connected to a counter electrode (not shown) with the liquid crystal cell interposed therebetween, and a common electrode line (not shown) common to all pixels (in the case of a Cs on Common structure) or an adjacent scanning signal line GL (Cs on Gate structure).

In the liquid crystal display device described above, the data signal line drive circuit 30 outputs a display data signal to each data signal line SL for each pixel or for each horizontal scanning period (1H line). Further, when the scanning signal sent on the scanning signal line GL becomes active, the thin film transistor 21 becomes conductive, whereby the display data signal sent on the data signal line SL is written to the pixel capacitor 22 as electric charge. . Then, the display is maintained by the charges written in the pixel capacitors 22.

In the liquid crystal display device, a data signal line driving circuit 30, a scanning signal line driving circuit 34, and the pixel array 19 are monolithically formed on a transparent insulating substrate such as glass (not shown). Therefore, the pixel array 1
9 are formed of a polycrystalline silicon thin film. Under the thin film transistors 4, at least the channel region and the vicinity of the junction of the thin film transistors 4 are shielded from light, as described in the first embodiment. The light-shielding film 3 made of chromium, titanium, tantalum, or the like is provided so as to face the gate electrode of the thin film transistor 4.

Further, as shown in FIG. 8, the light-shielding films 3 are electrically connected to each other by the transparent electrode layer 2 laid over the entire pixel array 19, and serve as potential stabilizing means. A constant voltage is applied from the ground wiring 12 and the DC power supply 13. As the transparent electrode layer 2, ITO or the like can be used. ITO
Has a heat resistance of 500 ° C. or more depending on the film forming conditions, and thus can be applied to a manufacturing process of a polycrystalline silicon thin film transistor.

With such a structure, the thin film transistor 4 of the liquid crystal display device is shielded from light by the light shielding film 3, and the light shielding film 3 has the characteristics of the thin film transistor 4 by the ground wiring 12 and the DC power supply 13. It is possible to apply a constant bias that does not have an adverse effect. Further, since the transparent electrode layer 2 extending over the entire surface of the pixel array 19 is used as a wiring for applying a bias to the light-shielding film 3, the wiring resistance can be suppressed low and a high light transmittance (aperture ratio) can be obtained. It can be maintained.

Further, in the case of the liquid crystal display device using the semiconductor device shown in FIG. 2, since the area of the light shielding films 3 is small, the aperture ratio of the liquid crystal display device can be further improved.

Incidentally, in FIG. 8, the transparent electrode layer 2
Are laid integrally on the entire pixel array 19, as shown in FIG. 9, the transparent electrode layer 2 is divided into a plurality of regions of the pixel array 19, and the divided regions are laid. The light shielding films 3 may be connected to each other to apply an optimum constant voltage to each of them.

In this case, even when there is a distribution (variation) in the characteristics of the pixel transistors in the pixel array 19, an optimal voltage can be applied to each region, so that the display quality can be improved. .

Although several examples of the present invention have been described above, the present invention is not limited to the above embodiments, but applies to all configurations based on the same concept.

[0065]

As described above, in the semiconductor device according to the first aspect of the present invention, the conductive light-shielding film that shields light from irradiating the channel region of the active layer of each thin-film transistor and the light-shielding film are interconnected. And a potential stabilizing means connected to the transparent electrode for stabilizing the potential of the light shielding film.

Therefore, the electrons jumping into the light-shielding film can be released to the potential stabilizing means via the transparent electrode, so that no charge is accumulated in the light-shielding film. Therefore, it is possible to prevent an unintended voltage from being applied to the thin film transistor due to the accumulation of the electric charge in the light shielding film.

As described above, in the semiconductor device according to the second aspect of the present invention, in addition to the configuration of the first aspect, the potential stabilizing means is constituted by a power supply for applying a predetermined voltage to the light shielding film.

Therefore, in addition to the effect of the first aspect, a predetermined voltage is applied to the light shielding film by the potential stabilizing means. Therefore, by selecting an optimal voltage for this, there is an effect that a decrease in the off characteristic (increase in leak current) and a decrease in reliability of the thin film transistor can be minimized.

According to a third aspect of the present invention, as described above, in addition to the configuration of the second aspect, the light shielding film is disposed at a position facing the gate electrode of the thin film transistor with respect to the channel region. Configuration.

Therefore, in addition to the effect of the configuration of claim 2, since no gate electrode exists between the light shielding film and the channel region, the electric field by the light shielding film is not shielded by the gate electrode. . Therefore, there is an effect that the threshold value of the thin film transistor can be easily controlled.

According to the image display device of the fourth aspect of the present invention, as described above, a plurality of display pixels are provided in a matrix on a transparent insulating substrate, and the display is performed by individually driving these pixels. In order to solve the above-described problem, the pixel includes a thin film transistor as a switching element for switching the pixel, and a conductive film that blocks irradiation of light to a channel region of an active layer of the thin film transistor. The light-shielding film includes a transparent electrode connected to the light-shielding film and connected to a potential stabilizing unit for stabilizing the potential of the light-shielding film.

Therefore, the electrons jumping into the light-shielding film of the thin film transistor flow out to the potential stabilizing means through the transparent electrode. Therefore, no charge is accumulated in the light-shielding film, and there is no possibility that an unintended voltage is applied to the channel. Further, since the wiring for letting out the electric charge jumping into the light shielding film is made of a transparent electrode, the aperture ratio does not decrease. As a result, it is possible to provide a liquid crystal display device having high reliability and excellent display quality.

According to a fifth aspect of the present invention, as described above, in addition to the configuration of the fourth aspect, the potential stabilizing means comprises a power supply for applying a predetermined voltage to the light shielding film. .

Therefore, in addition to the effect of the configuration of claim 4, a predetermined voltage is applied to the light-shielding film of the thin film transistor by the potential stabilizing means connected to the transparent electrode. By selecting an optimal value for the voltage applied to the light-shielding film, the threshold value of the thin film transistor can be shifted to an optimal value. Thus, a decrease in the off characteristic and a decrease in the reliability of the thin film transistor can be suppressed to a minimum. As a result, there is an effect that the retention rate and long-term reliability of the pixel can be improved.

According to a sixth aspect of the present invention, as described above, in addition to the configuration of the fourth or fifth aspect, the light-shielding film is located at a position facing the gate electrode of the thin film transistor with respect to the channel region. It is the structure arranged in.

Therefore, in addition to the effect of the fourth or fifth aspect, the electric field by the light-shielding film is not shielded by the gate electrode, so that the threshold value of the thin film transistor can be easily controlled. Thereby, there is an effect that the retention rate and long-term reliability of the pixel can be improved with low power.

According to a seventh aspect of the present invention, as described above, in addition to the constitutions of the fourth to sixth aspects, the transparent electrode is provided on the pixel array composed of the respective pixels. This is a configuration that is laid over the entire image forming surface.

Therefore, in addition to the effects of the fourth to sixth aspects, since the transparent electrode is laid over the entire surface of the pixel array, the resistance of the transparent electrode is reduced, and a stable voltage is obtained. There is an effect that the voltage can be applied to the light-shielding film.

Therefore, in addition to the effects of the fourth to sixth aspects, the respective light shielding films are connected to each other by the transparent electrodes laid over the entire image forming surface of the pixel array. If only one potential stabilizing means is provided, the potential can be stabilized for all the light shielding films. Further, since the transparent electrode is laid on the entire pixel forming surface of the pixel array on the pixel array composed of the respective pixels, the resistance of the transparent electrode is reduced, and the stable voltage is blocked by the light shielding. There is an effect that the voltage can be applied to the film.

As described above, the image display device according to the eighth aspect of the present invention, in addition to the configuration of the seventh aspect, is characterized in that:
The pixel array is divided into a plurality of portions, and the potential stabilizing means is connected to each of the divided transparent electrodes.

Therefore, in addition to the effect of the configuration of claim 7, the transparent electrode is laid in a plurality of regions of the pixel array, and in the divided regions,
The light-shielding films are connected to each other by the transparent electrode. Accordingly, even when the characteristics of the thin film transistors are distributed (varied) in the pixel array, it is possible to apply an optimal voltage to the light-shielding film in each region,
There is an effect that the display quality can be improved.

[Brief description of the drawings]

FIG. 1 illustrates one embodiment of the present invention, and is a cross-sectional view illustrating a structure of a semiconductor element of a semiconductor device.

FIG. 2 illustrates another example of the semiconductor device, and is a cross-sectional view illustrating a structure of a semiconductor element of the semiconductor device.

FIG. 3 shows still another example of the semiconductor device, and is a cross-sectional view showing a structure of a semiconductor element of the semiconductor device.

FIG. 4, showing another embodiment of the present invention, is a block diagram illustrating a structure of a main part of an image display device.

FIG. 5 is an explanatory diagram showing a circuit configuration of a data signal line driving circuit of the image display device.

FIG. 6 is an explanatory diagram showing a circuit configuration of a scanning signal line driving circuit of the image display device.

FIG. 7 is an explanatory diagram showing a structure of a pixel of the image display device.

FIG. 8 is a block diagram showing another example of the image display device shown in FIG. 4 and showing a structure of a main part of the image display device.

FIG. 9 is a block diagram showing still another example of the image display device and showing a structure of a main part of the image display device.

FIG. 10 is a block diagram showing a structure of a main part of a conventional image display device.

FIG. 11 is a block diagram showing still another example of the image display device and showing a structure of a main part of the image display device.

FIG. 12 is a cross-sectional view illustrating a structure of a semiconductor element of a conventional semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent insulating substrate 2 Transparent electrode layer (transparent electrode) 3 Shielding film 4 Thin film transistor 6 Polycrystalline silicon thin film (active layer) 6a Channel region 8 Gate electrode 12 Ground wiring (potential stabilizing means) 13 DC power supply (potential stabilization) Means) 19 pixel array 20 pixels

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-142851 (JP, A) JP-A-2-198429 (JP, A) JP-A-6-317809 (JP, A) JP-A-8-108 167719 (JP, A) JP-A-3-82081 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/786 G09F 9/35

Claims (8)

(57) [Claims] 1. A semiconductor device comprising a plurality of thin film transistors formed on a transparent insulating substrate, comprising: a conductive light-shielding film for shielding light irradiation on a channel region of an active layer of each of the thin film transistors; A semiconductor device comprising: a transparent electrode that connects light-shielding films to each other; and a potential stabilizing unit that is connected to the transparent electrode and stabilizes the potential of the light-shielding film. 2. The semiconductor device according to claim 1, wherein said potential stabilizing means comprises a power supply for applying a predetermined voltage to the light-shielding film. 3. The semiconductor device according to claim 2, wherein said light shielding film is arranged at a position facing said gate electrode of said thin film transistor with respect to said channel region. 4. An image display device in which a plurality of display pixels are provided in a matrix on a transparent insulating substrate, and each of the pixels is individually driven to perform display, A thin film transistor as a switching element for switching; a conductive light shielding film for shielding irradiation of light to a channel region of an active layer of the thin film transistor; and a stabilizing device that is connected to the light shielding film and stabilizes a potential of the light shielding film. And a transparent electrode connected to the potential stabilizing means. 5. The image display device according to claim 4, wherein said potential stabilizing means comprises a power supply for applying a predetermined voltage to the light shielding film. 6. The image display device according to claim 4, wherein the light-shielding film is arranged at a position facing the gate electrode of the thin-film transistor with respect to the channel region. 7. The apparatus according to claim 4, wherein said transparent electrode is laid on a pixel array comprising said pixels over the entire image forming surface of said pixel array.
An image display device according to any one of the above. 8. The apparatus according to claim 7, wherein said transparent electrode is divided into a plurality of parts on said pixel array, and said potential stabilizing means is connected to each of said divided transparent electrodes. The image display device as described in the above.