Abstract: In a manufacturing process of a transistor including an oxide semiconductor film, oxygen doping treatment is performed on the oxide semiconductor film, and then heat treatment is performed on the oxide semiconductor film and an aluminum oxide film provided over the oxide semiconductor film. Consequently, an oxide semiconductor film which includes a region containing more oxygen than a stoichiometric composition is formed. The transistor formed using the oxide semiconductor film can have high reliability because the amount of change in the threshold voltage of the transistor by a bias-temperature stress test (BT test) is reduced.

Abstract: A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. An oxide semiconductor film which can have a first crystal structure by heat treatment and an oxide semiconductor film which can have a second crystal structure by heat treatment are formed so as to be stacked, and then heat treatment is performed; accordingly, crystal growth occurs with the use of an oxide semiconductor film having the second crystal structure as a seed, so that an oxide semiconductor film having the first crystal structure is formed. An oxide semiconductor film formed in this manner is used for an active layer of the transistor.

Abstract: An object is to provide an oxide semiconductor having stable electric characteristics and a semiconductor device including the oxide semiconductor. A manufacturing method of a semiconductor film by a sputtering method includes the steps of holding a substrate in a treatment chamber which is kept in a reduced-pressure state; heating the substrate at lower than 400° C.; introducing a sputtering gas from which hydrogen and moisture are removed in the state where remaining moisture in the treatment chamber is removed; and forming an oxide semiconductor film over the substrate with use of a metal oxide which is provided in the treatment chamber as a target. When the oxide semiconductor film is formed, remaining moisture in a reaction atmosphere is removed; thus, the concentration of hydrogen and the concentration of hydride in the oxide semiconductor film can be reduced. Thus, the oxide semiconductor film can be stabilized.

Abstract: One of objects is to provide a semiconductor film having stable characteristics. Further, one of objects is to provide a semiconductor element having stable characteristics. Further, one of objects is to provide a semiconductor device having stable characteristics. Specifically, a structure which includes a seed crystal layer (seed layer) including crystals each having a first crystal structure, one of surfaces of which is in contact with an insulating surface, and an oxide semiconductor film including crystals growing anisotropically, which is on the other surface of the seed crystal layer (seed layer) may be provided. With such a heterostructure, electric characteristics of the semiconductor film can be stabilized.

Abstract: In a process of manufacturing a transistor including an oxide semiconductor layer, an amorphous oxide semiconductor layer which includes a region containing excess oxygen as compared to a stoichiometric composition ratio of an oxide semiconductor in a crystalline state is formed over a silicon oxide film, an aluminum oxide film is formed over the amorphous oxide semiconductor layer, and then heat treatment is performed so that at least part of the amorphous oxide semiconductor layer is crystallized and an oxide semiconductor layer which includes a crystal having a c-axis substantially perpendicular to a surface of the oxide semiconductor layer is formed.

Abstract: An object is to provide an oxide semiconductor having stable electric characteristics and a semiconductor device including the oxide semiconductor. A manufacturing method of a semiconductor film by a sputtering method includes the steps of holding a substrate in a treatment chamber which is kept in a reduced-pressure state; heating the substrate at lower than 400° C.; introducing a sputtering gas from which hydrogen and moisture are removed in the state where remaining moisture in the treatment chamber is removed; and forming an oxide semiconductor film over the substrate with use of a metal oxide which is provided in the treatment chamber as a target. When the oxide semiconductor film is formed, remaining moisture in a reaction atmosphere is removed; thus, the concentration of hydrogen and the concentration of hydride in the oxide semiconductor film can be reduced. Thus, the oxide semiconductor film can be stabilized.

Abstract: A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. An oxide semiconductor film which can have a first crystal structure by heat treatment and an oxide semiconductor film which can have a second crystal structure by heat treatment are formed so as to be stacked, and then heat treatment is performed; accordingly, crystal growth occurs with the use of an oxide semiconductor film having the second crystal structure as a seed, so that an oxide semiconductor film having the first crystal structure is formed. An oxide semiconductor film formed in this manner is used for an active layer of the transistor.

Abstract: In a thin film transistor which uses an oxide semiconductor, buffer layers containing indium, gallium, zinc, oxygen, and nitrogen are provided between the oxide semiconductor layer and the source and drain electrode layers.

Abstract: An object is to provide a thin film transistor and a method for manufacturing the thin film transistor including an oxide semiconductor with a controlled threshold voltage, high operation speed, a relatively easy manufacturing process, and sufficient reliability. An impurity having influence on carrier concentration in the oxide semiconductor layer, such as a hydrogen atom or a compound containing a hydrogen atom such as H2O, may be eliminated. An oxide insulating layer containing a large number of defects such as dangling bonds may be formed in contact with the oxide semiconductor layer, such that the impurity diffuses into the oxide insulating layer and the impurity concentration in the oxide semiconductor layer is reduced. The oxide semiconductor layer or the oxide insulating layer in contact with the oxide semiconductor layer may be formed in a deposition chamber which is evacuated with use of a cryopump whereby the impurity concentration is reduced.

Abstract: In a thin film transistor which uses an oxide semiconductor, buffer layers containing indium, gallium, zinc, oxygen, and nitrogen are provided between the oxide semiconductor layer and the source and drain electrode layers.

Abstract: It is an object of an embodiment of the present invention to reduce leakage current between a source and a drain in a transistor including an oxide semiconductor. As a first gate film in contact with a gate insulating film, a compound conductor which includes indium and nitrogen and whose band gap is less than 2.8 eV is used. Since this compound conductor has a work function of greater than or equal to 5 eV, preferably greater than or equal to 5.5 eV, the electron concentration in an oxide semiconductor film can be maintained extremely low. As a result, the leakage current between the source and the drain is reduced.

Abstract: An electrode formed using a transparent conductive oxide is likely to be crystallized by heat treatment performed in the manufacturing process of a semiconductor device. In the case of a thin film element using an electrode having a significantly uneven surface due to crystallization, a short circuit is likely to occur and thus reliability of the element is degraded. An object is to provide a light-transmitting conductive oxynitride which is not crystallized even if subjected to heat treatment and a manufacturing method thereof. It is found that an oxynitride containing indium, gallium, and zinc, to which hydrogen atoms are added as impurities, is a light-transmitting conductive film which is not crystallized even if heated at 350° C. and the object is achieved.

Abstract: There have been cases where transistors formed using oxide semiconductors are inferior in reliability to transistors formed using amorphous silicon. Thus, in the present invention, a semiconductor device including a highly reliable transistor formed using an oxide semiconductor is manufactured. An oxide semiconductor film is deposited by a sputtering method, using a sputtering target including an oxide semiconductor having crystallinity, and in which the direction of the c-axis of a crystal is parallel to a normal vector of the top surface of the oxide semiconductor. The target is formed by mixing raw materials so that its composition ratio can obtain a crystal structure.

Abstract: There have been cases where transistors formed using oxide semiconductors are inferior in reliability to transistors formed using amorphous silicon. Thus, in the present invention, a semiconductor device including a highly reliable transistor formed using an oxide semiconductor is manufactured. An oxide semiconductor film is deposited by a sputtering method, using a sputtering target including an oxide semiconductor having crystallinity, and in which the direction of the c-axis of a crystal is parallel to a normal vector of the top surface of the oxide semiconductor. The target is formed by mixing raw materials so that its composition ratio can obtain a crystal structure.

Abstract: In a thin film transistor which uses an oxide semiconductor, buffer layers containing indium, gallium, zinc, oxygen, and nitrogen are provided between the oxide semiconductor layer and the source and drain electrode layers.

Abstract: There have been cases where transistors formed using oxide semiconductors are inferior in reliability to transistors formed using amorphous silicon. Thus, in the present invention, a semiconductor device including a highly reliable transistor formed using an oxide semiconductor is manufactured. An oxide semiconductor film is deposited by a sputtering method, using a sputtering target including an oxide semiconductor having crystallinity, and in which the direction of the c-axis of a crystal is parallel to a normal vector of the top surface of the oxide semiconductor. The target is formed by mixing raw materials so that its composition ratio can obtain a crystal structure.

Abstract: To provide a highly reliable semiconductor device manufactured by giving stable electric characteristics to a semiconductor device including an oxide semiconductor. In a manufacturing process of a transistor, an oxide semiconductor layer, a source electrode layer, a drain electrode layer, a gate insulating film, a gate electrode layer, and an aluminum oxide film are formed in this order, and then heat treatment is performed on the oxide semiconductor layer and the aluminum oxide film, whereby an oxide semiconductor layer from which an impurity containing a hydrogen atom is removed and which includes a region containing oxygen more than the stoichiometric proportion is formed. In addition, when the aluminum oxide film is formed, entry and diffusion of water or hydrogen into the oxide semiconductor layer from the air due to heat treatment in a manufacturing process of a semiconductor device or an electronic appliance including the transistor can be prevented.

Abstract: In the transistor including an oxide semiconductor film, which includes a film for capturing hydrogen from the oxide semiconductor film (a hydrogen capture film) and a film for diffusing hydrogen (a hydrogen permeable film), hydrogen is transferred from the oxide semiconductor film to the hydrogen capture film through the hydrogen permeable film by heat treatment. Specifically, a base film or a protective film of the transistor including an oxide semiconductor film has a stacked-layer structure of the hydrogen capture film and the hydrogen permeable film. At this time, the hydrogen permeable film is formed on a side which is in contact with the oxide semiconductor film. After that, hydrogen released from the oxide semiconductor film is transferred to the hydrogen capture film through the hydrogen permeable film by the heat treatment.

Abstract: A semiconductor device having excellent electric characteristics and a method for manufacturing the semiconductor device are provided. A method for manufacturing a semiconductor device includes the steps of: forming a gate electrode; forming a gate insulating film to cover the gate electrode; forming an oxide semiconductor film over the gate insulating film; forming a hydrogen permeable film over the oxide semiconductor film; forming a hydrogen capture film over the hydrogen permeable film; performing heat treatment to release hydrogen from the oxide semiconductor film; forming a source electrode and a drain electrode to be in contact with a part of the oxide semiconductor film; and removing an exposed portion of the hydrogen capture film to form a channel protective film formed of the hydrogen permeable film. A semiconductor device manufactured by the above method is also provided.

Abstract: A method for forming an oxide semiconductor film having favorable semiconductor characteristics is provided. In addition, a method for manufacturing a semiconductor device having favorable electric characteristics, with use of the oxide semiconductor film is provided. A method for forming an oxide semiconductor film including the steps of forming an oxide semiconductor film, forming a hydrogen permeable film over and in contact with the oxide semiconductor film, forming a hydrogen capture film over and in contact with the hydrogen permeable film, and releasing hydrogen from the oxide semiconductor film by performing heat treatment. Further, in a method for manufacturing a semiconductor device, the method for forming an oxide semiconductor film is used.