67results about How to "Off-current can be reduced" patented technology

The present invention provides a display device which can display characters clearly and display images smoothly. An area gray scale method is adopted and a configuration of one pixel is changed depending on a mode, by selecting one or more display regions in each pixel. When characters are needed to be displayed clearly, one pixel is configured by selecting a stripe arrangement. Thus, clear display can be conducted. When images are needed to be displayed, one pixel is configured by selecting an indented state. Thus, smooth display can be conducted.

An object of the invention is to provide a display device which can reduce the number of times signal writing to a pixel is carried out and power consumption. A display device which can reduce the number of times signal writing to a pixel is carried out and power consumption can be provided. According to an active matrix display device of the invention, in the case a signal to be written to a pixel row is identical with a signal stored in the pixel row, the scan line driver circuit does not output a selecting pulse to a scan line corresponding to the pixel row, and the signal line driver circuit makes the signal lines in a floating state or keeps without changing the state of the signal line from the previous state.

A thin film transistor includes, as a buffer layer, a semiconductor layer which contains nitrogen and includes crystal regions in an amorphous structure between a gate insulating layer and source and drain regions, at least on the source and drain regions side. As compared to a thin film transistor in which an amorphous semiconductor is included in a channel formation region, on-current of a thin film transistor can be increased. In addition, as compared to a thin film transistor in which a microcrystalline semiconductor is included in a channel formation region, off-current of a thin film transistor can be reduced.

In an active matrix display device, a circuit including at least five thin film transistors (TFTs) which are provided with an approximately M-shaped semiconductor region for a single pixel electrode and gate lines and a capacitances line which cross the M-shaped semiconductor region, is used as a switching element. Each of the TFT have offset regions and lightly doped drain (LDD) regions. Then, by supplying a selection signal to the gate lines, the TFTs are operated, thereby writing data to the pixel, while a suitable voltage is supplied to the capacitance line, a channel is formed thereunder and it becomes a capacitor. Thus the amount of discharge from the pixel electrode is reduced by the capacitor.

A load, a transistor which controls a current value supplied to the load, a capacitor, a power supply line, and first to third switches are provided. After a threshold voltage of the transistor is held by the capacitor, a potential in accordance with a video signal is inputted and a voltage that is the sum of the threshold voltage and the potential is held. Accordingly, variation in current value caused by variation in threshold voltage of the transistor can be suppressed. Therefore, a desired current can be supplied to a load such as a light emitting element. In addition, a display device with a high duty ratio can be provided by changing a potential of the power supply line.

One feature of the present invention includes first to third steps of holding a voltage, corresponding to a difference between a voltage applied to a first power supply line and a threshold voltage of a first transistor, between both electrodes of first and second storage capacitors; holding a voltage, corresponding to a difference between a voltage applied to the first power supply line and a gate-source voltage of the first transistor, which is necessary to supply a light-emitting element with a current equivalent to a video signal current inputted into a signal line, between both the electrodes of the second storage capacitor; and applying a voltage based on the voltage held in the first and second storage capacitors in the first and second steps to a gate electrode of the first transistor; therefore, a current is supplied to the light-emitting element through the first transistor.

According to some embodiments, a semiconductor device includes a lower semiconductor substrate, an upper silicon pattern, and a MOS transistor. The MOS transistor includes a body region formed within the upper silicon pattern and source / drain regions separated by the body region. A buried insulating layer is interposed between the lower semiconductor substrate and the upper silicon pattern. A through plug penetrates the buried insulating layer and electrically connects the body region with the lower semiconductor substrate, the through plug positioned closer to one of the source / drain regions than the other source / drain region. At least some portion of the upper surface of the through plug is positioned outside a depletion layer when a source voltage is applied to the one of the source / drain regions, and the upper surface of the through plug is positioned inside the depletion layer when a drain voltage is applied to the one region.

It is an object of the present invention to reduce a cause of pseudo contour when display is performed with a time gray scale method. According to the present invention, one pixel is divided into m sub-pixels so that an area ratio of each sub-pixel becomes 20:21:22: . . . :2m−3:2m−2:2m−1 (m is an integer number of m≧2), and one frame is divided into n sub-frames so that a ratio of a lighting period in each sub-frame becomes 20:2m:22m: . . . :2(n−3)m:2(n−2)m:2(n−1)m (n is an integer number of n≧2). Then, a gray scale is expressed by controlling a manner of lighting in each of the m sub-pixels in each of the n sub-frames.

A semiconductor device which can operate normally even when the communication distance is extremely short, and which stores excess electric power which is not needed for circuit operation of the semiconductor device when a large amount of electric power is supplied thereto. The following are included: an antenna; a first AC / DC converter circuit which is connected to the antenna; a second AC / DC converter circuit which is connected to the antenna through a switching element; a detecting circuit which controls operation of the switching element in accordance with the value of a voltage output from the first AC / DC converter circuit; and a battery which stores electric power supplied from the antenna through the second AC / DC converter circuit. When the switching element is operated, electric power supplied from outside is at least partly supplied to the battery through the second AC / DC converter circuit.

A thin film transistor which includes a microcrystalline semiconductor film over a gate electrode with a gate insulating film interposed therebetween to be in an inner region in which end portions of microcrystalline semiconductor film are in an inside of end portions of the gate electrode, an amorphous semiconductor film which covers top and side surfaces of the microcrystalline semiconductor film, and an impurity semiconductor film to which an impurity element imparting one conductivity is added, and which forms a source region and a drain region, wherein the microcrystalline semiconductor film includes an impurity element serving as a donor is provided to reduce off current of a thin film transistor, to reduce reverse bias current of a diode, and to improve an image quality of a display device using a thin film transistor.

A semiconductor device including a non-volatile memory cell including a writing transistor which includes an oxide semiconductor, a reading transistor which includes a semiconductor material different from that of the writing transistor, and a capacitor is provided. Data is written or rewritten to the memory cell by turning on the writing transistor and supplying a potential to a node where a source electrode (or a drain electrode) of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected to each other, and then turning off the writing transistor so that the predetermined amount of charge is held in the node. Further, when a transistor whose threshold voltage is controlled and set to a positive voltage is used as the reading transistor, a reading potential is a positive potential.

A thin film transistor (TFT) and the method of forming the same is provided. The method of forming the TFT on a surface of a substrate, includes the steps of: forming a gate electrode; deposing a gate dielectric on the gate electrode; forming a nanocrystalline silicon (nc-Si) layer and an amorphous silicon (a-Si:H) layer above the gate dielectric, so that the thickness of the nc-Si layer is less than 30 nm thereby reducing off-current; and forming a source / drain electrode. The TFT includes: a gate electrode on a substrate, a gate dielectric on the gate electrode; a nc-Si layer having a thickness less than 30 nm, thereby reducing off-current; an a-Si:H layer; and a source / drain electrode.

A thin film transistor includes, as a buffer layer, an amorphous semiconductor layer having nitrogen or an NH group between a gate insulating layer and source and drain regions and at least on the source and drain regions side. As compared to a thin film transistor in which an amorphous semiconductor is included in a channel formation region, on-current of a thin film transistor can be increased. In addition, as compared to a thin film transistor in which a microcrystalline semiconductor is included in a channel formation region, off-current of a thin film transistor can be reduced.

A load, a transistor which controls a current value supplied to the load, a capacitor, a power supply line, and first to third switches are provided. After a threshold voltage of the transistor is held by the capacitor, a potential in accordance with a video signal is inputted and a voltage that is the sum of the threshold voltage and the potential is held. Accordingly, variation in current value caused by variation in threshold voltage of the transistor can be suppressed. Therefore, a desired current can be supplied to a load such as a light emitting element. In addition, a display device with a high duty ratio can be provided by changing a potential of the power supply line.

In relation to reading of data in a memory, it is an object to provide a semiconductor device mounted with a low power consumption memory. A semiconductor device including a word line, a bit line, and a memory cell electrically connected to the word line and the bit line, further includes a precharge circuit for making the bit line have an electric potential for reading data stored in the memory cell. The precharge circuit is provided for each bit line and connected to the bit line. Further, the precharge circuit is capable of making each bit line have an electric potential for reading the data stored in the memory cell for each bit line.

A circuit board includes: a substrate; source and drain electrodes formed on the substrate; an organic semiconductor layer formed on the source and drain electrodes; a gate insulating layer formed on the organic semiconductor layer; and a gate electrode formed on the gate insulating layer, wherein: the substrate includes a first part, a second part, and a third part interposed between the first and second parts and a thickness of the first part or a thickness of the second part is greater than that of the third part; the source electrode is formed on the first part; the drain electrode is formed on the second part; a part of the organic semiconductor layer is formed on the third part; and a thickness of the gate insulating layer disposed on the first and second parts is smaller than that of the gate insulating layer disposed on the third part.

To provide a display device whose display can be recognized even in dark places or under the strong outside light. The display device performs display by controlling the number of gray scales in accordance with the intensity of outside light, which means a display mode can be switched in accordance with the data to be displayed on the display screen. A video signal generation circuit is controlled in each display mode in such a manner that it directly outputs an input video signal with an analog value, outputs a signal with a binary digital value, or outputs a signal with a multivalued digital value. As a result, gray scales displayed in pixels are timely changed. Accordingly, clear images can be displayed while maintaining high visibility in various environments, in the wide range from, for example, dark places or indoors (e.g., under a fluorescent lighting) to outdoors (e.g., under the sunlight).

The invention provides a thin film transistor that can reduce an off-current flowing in end-parts in a channel width direction of a channel layer and a manufacturing method therefor.Widths of a source electrode (160a) and a drain electrode (160b) are smaller than a width of a channel layer (140). Accordingly, in the channel layer (140), low resistance regions (140b) are formed to surround respectively the source electrode (160a) and the drain electrode (160b). A high resistance region (140a) having a higher resistance value than those of the low resistance regions (140b) remains not only in the region sandwiched between the two low resistance regions (140b), but also in the end parts in the channel width direction. As a result, in a TFT (100), the high resistance region (140a) is extended not only to the channel region sandwiched between the source electrode (160a) and the drain electrode (160b), but also to the end parts in the channel width direction. Accordingly, the off-current flowing through the end parts in the channel width direction reduces.

Disclosed is a display device including a transistor showing extremely low off current. In order to reduce the off current, a semiconductor material whose band gap is greater than that of a silicon semiconductor is used for forming a transistor, and the concentration of an impurity which serves as a carrier donor of the semiconductor material is reduced. Specifically, an oxide semiconductor whose band gap is greater than or equal to 2 eV, preferably greater than or equal to 2.5 eV, more preferably greater than or equal to 3 eV is used for a semiconductor layer of a transistor, and the concentration of an impurity which serves as a carrier donor included is reduced. Consequently, the off current of the transistor per micrometer in channel width can be reduced to lower than 10 zA / μm at room temperature and lower than 100 zA / μm at 85° C.

A semiconductor device 10 according to the present invention includes an active layer 14 supported on a substrate 11 and having two channel regions 14c1, 14c2, a source region 14s, a drain region 14d, and an intermediate region 14m formed between the two channel regions 14c1, 14c2; a contact layer 16 having a source contact region 16s, a drain contact region 16d, and an intermediate contact region 16m; a source electrode 18s; a drain electrode 18d; an intermediate electrode 18m; and a gate electrode 12 facing the two channel regions and the intermediate region through a gate insulating film 13 interposed therebetween. An entire portion of the intermediate electrode 18m that is located between the first channel region 14c1 and the second channel region 14c2 overlaps the gate electrode 12 through the intermediate region 14m and the gate insulating film 13.

An organic transistor includes a substrate; a gate electrode and a gate insulating film sequentially formed on the substrate in the stated order; and a source electrode, a drain electrode, and an organic semiconductor layer formed on at least the gate insulating film. Ultraviolet light is radiated to the substrate from a side without the gate electrode, transmitted through the substrate and the gate insulating film, reflected at the gate electrode, and absorbed at the organic semiconductor layer. Conductivity of the organic semiconductor layer that has absorbed the ultraviolet light is lower than that of the organic semiconductor layer that has not absorbed the ultraviolet light.

An object is to provide a method for manufacturing a thin film transistor having favorable electric characteristics, with high productivity. A gate electrode is formed over a substrate and a gate insulating layer is formed over the gate electrode. A first semiconductor layer is formed over the gate insulating layer by generating plasma using a deposition gas containing silicon or germanium, hydrogen, and a rare gas. Next, a second semiconductor layer including an amorphous semiconductor and a microcrystal semiconductor is formed in such a manner that the first semiconductor layer is partially grown as a seed crystal by generating plasma using a deposition gas containing silicon or germanium, hydrogen, and a gas containing nitrogen. Then, a semiconductor layer to which an impurity imparting one conductivity is added is formed and a conductive film is formed. Thus, a thin film transistor is manufactured.

One object of the present invention is reduction of off current of a thin film transistor. Another object of the present invention is improvement of electric characteristics of the thin film transistor. Further, another object of the present invention is improvement of image quality of the display device including the thin film transistor. The thin film transistor includes a semiconductor film containing germanium at a concentration greater than or equal to 5 at. % and less than or equal to 100 at. % or a conductive film which is provided over a gate electrode with the gate insulating film interposed therebetween and which is provided in an inner region of the gate electrode so as not to overlap with an end portion of the gate electrode, a film covering at least a side surface of the semiconductor film containing germanium at a concentration greater than or equal to 5 at. % and less than or equal to 100 at. % or the conductive film, a pair of wirings formed over the film covering the side surface of the semiconductor film containing germanium at a concentration greater than or equal to 5 at. % and less than or equal to 100 at. % or the conductive film.

A display device includes a scan line extending in a first direction, a data line and a driving voltage line extending in a second direction crossing the first direction, a switching thin film transistor (“TFT”) connected to the scan line and the data line, a driving TFT connected to the switching TFT and including a driving semiconductor layer and a driving gate electrode, a storage capacitor connected to the driving TFT and including first and second storage capacitor plates, a node connection line between the data line and the driving voltage line and connected to the driving gate electrode, and a shielding portion between the data line and the node connection line.

A thin film transistor includes a gate insulating layer covering a gate electrode, a semiconductor layer in contact with the gate insulating layer, and impurity semiconductor layers which are in contact with part of the semiconductor layer and which form a source region and a drain region. The semiconductor layer includes a microcrystalline semiconductor layer formed on the gate insulating layer and a microcrystalline semiconductor region containing nitrogen in contact with the microcrystalline semiconductor layer. The thin film transistor in which off-current is small and on-current is large can be manufactured with high productivity.

A system for reducing an OFF-current in a thin film transistor of a liquid crystal display device includes gate and data lines crossing each other, a pixel thin film transistor including gate, source and drain electrodes, the gate electrode connected to the gate line and the source electrode connected to the data line, a liquid crystal capacitor connected to the drain electrode of the pixel thin film transistor, a first switch thin film transistor connected to a first end of the data line, a second switch thin film transistor connected to a first end of the gate line, a first voltage source electrically connected to the drain electrode of the pixel thin film transistor, a second voltage source connected to a source electrode of the first switch thin film transistor, a third voltage source connected to gate electrodes of the first and second switch thin film transistors, and a fourth voltage source connected to a source electrode of the second switch thin film transistor.