Abstract: A transistor includes a gate, a source, and a drain, the gate is electrically connected to the source or the drain, a first signal is input to one of the source and the drain, and an oxide semiconductor layer whose carrier concentration is 5×1014/cm3 or less is used for a channel formation layer. A capacitor includes a first electrode and a second electrode, the first electrode is electrically connected to the other of the source and the drain of the transistor, and a second signal which is a clock signal is input to the second electrode. A voltage of the first signal is stepped up or down to obtain a third signal which is output as an output signal through the other of the source and the drain of the transistor.

Abstract: Reducing hydrogen concentration in a channel formation region of an oxide semiconductor is important in stabilizing threshold voltage of a transistor including an oxide semiconductor and improving reliability. Hence, hydrogen is attracted from the oxide semiconductor and trapped in a region of an insulating film which overlaps with a source region and a drain region of the oxide semiconductor. Impurities such as argon, nitrogen, carbon, phosphorus, or boron are added to the region of the insulating film which overlaps with the source region and the drain region of the oxide semiconductor, thereby generating a defect. Hydrogen in the oxide semiconductor is attracted to the defect in the insulating film. The defect in the insulating film is stabilized by the presence of hydrogen.

Abstract: An oxide semiconductor stacked film which does not easily cause a variation in electrical characteristics of a transistor and has high stability is provided. Further, a transistor which includes the oxide semiconductor stacked film in its channel formation region and has stable electrical characteristics is provided. An oxide semiconductor stacked film includes a first oxide semiconductor layer, a second oxide semiconductor layer, and a third oxide semiconductor layer which are sequentially stacked and each of which contains indium, gallium, and zinc. The content percentage of indium in the second oxide semiconductor layer is higher than that in the first oxide semiconductor layer and the third oxide semiconductor layer, and the absorption coefficient of the oxide semiconductor stacked film, which is measured by the CPM, is lower than or equal to 3×10?3/cm in an energy range of 1.5 eV to 2.3 eV.

Abstract: An object is to improve reliability of a semiconductor device. A semiconductor device including a driver circuit portion and a display portion (also referred to as a pixel portion) over the same substrate is provided. The driver circuit portion and the display portion include thin film transistors in which a semiconductor layer includes an oxide semiconductor; a first wiring; and a second wiring. The thin film transistors each include a source electrode layer and a drain electrode layer. In the thin film transistor in the driver circuit portion, the semiconductor layer is sandwiched between a gate electrode layer and a conductive layer. The first wiring and the second wiring are electrically connected to each other in an opening provided in a gate insulating film through an oxide conductive layer.

Abstract: To improve switching characteristics of a transistor in which a channel is formed in an oxide semiconductor layer. A parasitic channel is formed at an end portion of the oxide semiconductor layer because a source and a drain of the transistor are electrically connected to the end portion. That is, when at least one of the source and the drain of the transistor is not electrically connected to the end portion, the parasitic channel is not formed at the end portion. In view of this, a transistor having a structure in which at least one of a source and a drain of the transistor is not or less likely to be electrically connected to an end portion of an oxide semiconductor layer is provided.

Abstract: It is an object to provide a manufacturing method of a structure of a thin film transistor including an oxide semiconductor film, in which threshold voltage at which a channel is formed is positive and as close to 0 V as possible. A protective insulating layer is formed to cover a thin film transistor including an oxide semiconductor layer that is dehydrated or dehydrogenated by first heat treatment, and second heat treatment at a temperature that is lower than that of the first heat treatment, in which the increase and decrease in temperature are repeated plural times, is performed, whereby a thin film transistor including an oxide semiconductor layer, in which threshold voltage at which a channel is formed is positive and as close to 0 V as possible without depending on the channel length, can be manufactured.

Abstract: A semiconductor device includes a semiconductor layer, a gate electrode overlapping with the semiconductor layer, a first gate insulating layer between the semiconductor layer and the gate electrode, and a second gate insulating layer between the first gate insulating layer and the gate electrode. The first gate insulating layer includes an oxide in which the nitrogen content is lower than or equal to 5 at. %, and the second gate insulating layer includes charge trap states.

Abstract: To reduce a leakage current of a transistor so that malfunction of a logic circuit can be suppressed. The logic circuit includes a transistor which includes an oxide semiconductor layer having a function of a channel formation layer and in which an off current is 1×10?13 A or less per micrometer in channel width. A first signal, a second signal, and a third signal that is a clock signal are input as input signals. A fourth signal and a fifth signal whose voltage states are set in accordance with the first to third signals which have been input are output as output signals.

Abstract: To suppress a decrease in on-state current in a semiconductor device including an oxide semiconductor. A semiconductor device includes an insulating film containing silicon, an oxide semiconductor film over the insulating film, a gate insulating film containing silicon over the oxide semiconductor film, a gate electrode which is over the gate insulating film and overlaps with at least the oxide semiconductor film, and a source electrode and a drain electrode which are electrically connected to the oxide semiconductor film. In the semiconductor device, the oxide semiconductor film which overlaps with at least the gate electrode includes a region in which a concentration of silicon distributed from an interface with the insulating film is lower than or equal to 1.1 at. %. In addition, a concentration of silicon contained in a remaining portion of the oxide semiconductor film except the region is lower than the concentration of silicon contained in the region.

Abstract: A crystalline oxide semiconductor film which can be used as a semiconductor film of a transistor or the like is provided. In particular, a crystalline oxide semiconductor film with less defects such as grain boundaries is provided. One embodiment of the present invention is a crystalline oxide semiconductor film which is provided over a substrate and has a region including five or less areas where a transmission electron diffraction pattern showing discontinuous points is observed when an observation area is changed one-dimensionally within a range of 700 nm, using a transmission electron diffraction apparatus with an electron beam having a probe diameter of 1 nm.

Abstract: The band tail state and defects in the band gap are reduced as much as possible, whereby optical absorption of energy which is in the vicinity of the band gap or less than or equal to the band gap is reduced. In that case, not by merely optimizing conditions of manufacturing an oxide semiconductor film, but by making an oxide semiconductor to be a substantially intrinsic semiconductor or extremely close to an intrinsic semiconductor, defects on which irradiation light acts are reduced and the effect of light irradiation is reduced essentially. That is, even in the case where light with a wavelength of 350 nm is delivered at 1×1013 photons/cm2·sec, a channel region of a transistor is formed using an oxide semiconductor, in which the absolute value of the amount of the variation in the threshold voltage is less than or equal to 0.65 V.

Abstract: An object is to manufacture a semiconductor device including an oxide semiconductor film, which has stable electric characteristics and high reliability. A crystalline oxide semiconductor film is formed, without performing a plurality of steps, as follows: by utilizing a difference in atomic weight of plural kinds of atoms included in an oxide semiconductor target, zinc with low atomic weight is preferentially deposited on an oxide insulating film to form a seed crystal including zinc; and tin, indium, or the like with high atomic weight is deposited on the seed crystal while causing crystal growth. Further, a crystalline oxide semiconductor film is formed by causing crystal growth using a seed crystal with a hexagonal crystal structure including zinc as a nucleus, whereby a single crystal oxide semiconductor film or a substantially single crystal oxide semiconductor film is formed.

Abstract: In a bottom-gate thin film transistor using the stack of the first oxide semiconductor layer and the second oxide semiconductor layer, an oxide insulating layer serving as a channel protective layer is formed over and in contact with part of the oxide semiconductor layer overlapping with a gate electrode layer. In the same step as formation of the insulating layer, an oxide insulating layer covering a peripheral portion (including a side surface) of the stack of the oxide semiconductor layers is formed.

Abstract: An object is to provide a display device with excellent display characteristics, where a pixel circuit and a driver circuit provided over one substrate are formed using transistors which have different structures corresponding to characteristics of the respective circuits. The driver circuit portion includes a driver circuit transistor in which a gate electrode layer, a source electrode layer, and a drain electrode layer are formed using a metal film, and a channel layer is formed using an oxide semiconductor. The pixel portion includes a pixel transistor in which a gate electrode layer, a source electrode layer, and a drain electrode layer are formed using an oxide conductor, and a semiconductor layer is formed using an oxide semiconductor. The pixel transistor is formed using a light-transmitting material, and thus, a display device with higher aperture ratio can be manufactured.

Abstract: An imaging device that is highly stable to irradiation with radial rays such as X-rays and can inhibit a decrease in electrical characteristics is provided. The imaging device takes an image with radial rays such as X-rays and includes pixel circuits arranged in a matrix and a scintillator overlapping the pixel circuits. The pixel circuits each includes a switching transistor with an extremely small off-state current and a light-receiving element which is configured to convert the radial rays to electrical charges. A gate insulating film of the switching transistor has a stacked structure including a silicon nitride film with a thickness of 100 nm to 400 nm and a silicon oxide film or a silicon oxynitride film with a thickness of 5 nm to 20 nm.

Abstract: In a liquid crystal display device including a plurality of pixels in a display portion and configured to performed display in a plurality of frame periods, each of the frame periods includes a writing period and a holding period, and after an image signal is input to each of the plurality of pixels in the writing period, a transistor included in each of the plurality of pixels is turned off and the image signal is held for at least 30 seconds in the holding period. The pixel includes a semiconductor layer including an oxide semiconductor layer, and the oxide semiconductor layer has a carrier concentration of less than 1×1014/cm3.

Abstract: To provide a method for manufacturing a thin film transistor in which contact resistance between an oxide semiconductor layer and source and drain electrode layers is small, the surfaces of the source and drain electrode layers are subjected to sputtering treatment with plasma and an oxide semiconductor layer containing In, Ga, and Zn is formed successively over the source and drain electrode layers without exposure of the source and drain electrode layers to air.

Abstract: An object is to provide a semiconductor device including an oxide semiconductor film, which has stable electrical characteristics and high reliability. A stack of first and second material films is formed by forming the first material film (a film having a hexagonal crystal structure) having a thickness of 1 nm to 10 nm over an insulating surface and forming the second material film having a hexagonal crystal structure (a crystalline oxide semiconductor film) using the first material film as a nucleus. As the first material film, a material film having a wurtzite crystal structure (e.g., gallium nitride or aluminum nitride) or a material film having a corundum crystal structure (?-Al2O3, ?-Ga2O3, In2O3, Ti2O3, V2O3, Cr2O3, or ?-Fe2O3) is used.

Abstract: Manufactured is a transistor including an oxide semiconductor layer, a source electrode layer and a drain electrode layer overlapping with part of the oxide semiconductor layer, a gate insulating layer overlapping with the oxide semiconductor layer, the source electrode layer, and the drain electrode layer, and a gate electrode overlapping with part of the oxide semiconductor layer with the gate insulating layer provided therebetween, wherein, after the oxide semiconductor layer which is to be a channel formation region is irradiated with light and the light irradiation is stopped, a relaxation time of carriers in photoresponse characteristics of the oxide semiconductor layer has at least two kinds of modes: ?1 and ?2, ?1<?2 is satisfied, and ?2 is 300 seconds or less. In addition, a semiconductor device including the transistor is manufactured.

Abstract: It is an object to provide a manufacturing method of a structure of a thin film transistor including an oxide semiconductor film, in which threshold voltage at which a channel is formed is positive and as close to 0 V as possible. A protective insulating layer is formed to cover a thin film transistor including an oxide semiconductor layer that is dehydrated or dehydrogenated by first heat treatment, and second heat treatment at a temperature that is lower than that of the first heat treatment, in which the increase and decrease in temperature are repeated plural times, is performed, whereby a thin film transistor including an oxide semiconductor layer, in which threshold voltage at which a channel is formed is positive and as close to 0 V as possible without depending on the channel length, can be manufactured.