Abstract: A method for etching is provided in which the etching selectivity of an amorphous semiconductor film to a crystalline semiconductor film is high. Part of a stacked semiconductor film in which an amorphous semiconductor film is provided on a crystalline semiconductor film is etched using a mixed gas of a Br-based gas, a F-based gas, and an oxygen gas, so that part of the crystalline semiconductor film provided in the stacked semiconductor film is exposed. Reduction in the film thickness of the exposed portion can be suppressed by performing the etching in such a manner. Moreover, when etching for forming a back channel portion of a thin film transistor is performed with the method for etching, favorable electric characteristics of the thin film transistor can be obtained. An insulating layer is preferably provided over the thin film transistor.

Abstract: It is an object to form a high quality gate insulating film which is dense and has a strong insulation resistance property, and to propose a high reliable organic transistor in which a tunnel leakage current is little. One mode of the organic transistor of the present invention has a step of forming the gate insulating film by forming the conductive layer which becomes the gate electrode activating oxygen (or gas including oxygen) or nitrogen (or gas including nitrogen) or the like using dense plasma in which density of electron is 1011 cm?3 or more, and electron temperature is a range of 0.2 eV to 2.0 eV with plasma activation, and reacting directly with a portion of the conductive layer which becomes the gate electrode to be insulated.

Abstract: It is an object of the present invention to provide an organic transistor having a low drive voltage. It is also another object of the present invention to provide an organic transistor, in which light emission can be obtained, which can be manufactured simply and easily. According to an organic light-emitting transistor, a composite layer containing an organic compound having a hole-transporting property and a metal oxide is used as part of the electrode that injects holes among source and drain electrodes, and a composite layer containing an organic compound having an electron-transporting property and an alkaline metal or an alkaline earth metal is used as part of the electrode that injects electrons, where either composite layer has a structure of being in contact with an organic semiconductor layer.

Abstract: An embodiment is a thin film transistor which includes a gate electrode layer, a gate insulating layer provided so as to cover the gate electrode layer; a first semiconductor layer entirely overlapped with the gate electrode layer; a second semiconductor layer provided over and in contact with the first semiconductor layer and having a lower carrier mobility than the first semiconductor layer; an impurity semiconductor layer provided in contact with the second semiconductor layer; a sidewall insulating layer provided so as to cover at least a sidewall of the first semiconductor layer; and a source and drain electrode layers provided in contact with at least the impurity semiconductor layer. The second semiconductor layer may consist of parts which are apart from each other over the first semiconductor layer.

Abstract: It is an object to provide an electrode for an organic field-effect transistor having a semiconductor layer formed of an organic semiconductor material (in the present invention, referred to as an organic field-effect transistor), which can reduce the energy barrier at an interface with the semiconductor layer. A composite layer including an organic compound and a metal oxide is used for the electrode for the organic field-effect transistor, in other words the composite layer is used for at least a part of either a source electrode or a drain electrode in the organic field-effect transistor.

Abstract: A thin film transistor in which an effect of photo current is small and an On/Off ratio is high is provided. In a bottom-gate bottom-contact (coplanar) thin film transistor, a channel formation region overlaps with a gate electrode, a first impurity semiconductor layer is provided between the channel formation region and a second impurity semiconductor layer which is in contact with a wiring layer. A semiconductor layer which serves as the channel formation region and the first impurity semiconductor layer preferably overlap with each other in a region where they overlap with the gate electrode. The first impurity semiconductor layer and the second impurity semiconductor layer preferably overlap with each other in a region where they do not overlap with the gate electrode.

Abstract: It is an object of the present invention to form an organic transistor including an organic semiconductor having high crystallinity without loosing an interface between an organic semiconductor of a channel where carriers are spread out and a gate insulating layer and deteriorating a yield. A semiconductor device according to the present invention has a stacked structure of organic semiconductor layers, and at least the upper organic semiconductor layer is in a polycrystalline or a single crystalline state and the lower organic semiconductor layer is made of a material serving as a channel. Carrier mobility can be increased owing to the upper organic semiconductor layer having high crystallinity; thus, insufficient contact due to the upper organic semiconductor layer can be compensated by the lower organic semiconductor layer.

Abstract: It is an object to provide an organic field effect transistor including an electrode which can reduce an energy barrier at an interface between a conductive layer and a semiconductor layer, and a semiconductor device including the organic field effect transistor. A composite layer containing an organic compound and an inorganic compound is provided in at least part of one of a source electrode and a drain electrode in an organic field effect transistor, and as the organic compound, a carbazole derivative represented by the general formula (1) is used. By providing the composite layer in at least part of one of the source electrode and the drain electrode, an energy barrier at an interface between a conductive layer and a semiconductor layer can be reduced.

Abstract: It is an object to form a high quality gate insulating film which is dense and has a strong insulation resistance property, and to propose a high reliable organic transistor in which a tunnel leakage current is little. One mode of the organic transistor of the present invention has a step of forming the gate insulating film by forming the conductive layer which becomes the gate electrode activating oxygen (or gas including oxygen) or nitrogen (or gas including nitrogen) or the like using dense plasma in which density of electron is 1011 cm?3 or more, and electron temperature is a range of 0.2 eV to 2.0 eV with plasma activation, and reacting directly with a portion of the conductive layer which becomes the gate electrode to be insulated.

Abstract: To provide a method for manufacturing a transistor which has little variation in characteristics and favorable electric characteristics. A gate insulating film is formed over a gate electrode; a semiconductor layer including a microcrystalline semiconductor is formed over the gate insulating film; an impurity semiconductor layer is formed over the semiconductor layer; a mask is formed over the impurity semiconductor layer, and then the semiconductor layer and the impurity semiconductor layer are etched with use of the mask to form a semiconductor stacked body; the mask is removed and then the semiconductor stacked body is exposed to plasma generated in an atmosphere containing a rare gas to form a barrier region on a side surface of the semiconductor stacked body; and a wiring over the impurity semiconductor layer of the semiconductor stacked body is formed.

Abstract: It is an object of the present invention to provide an organic transistor having a low drive voltage. It is also another object of the present invention to provide an organic transistor, in which light emission can be obtained, which can be manufactured simply and easily. According to an organic light-emitting transistor, a composite layer containing an organic compound having a hole-transporting property and a metal oxide is used as part of the electrode that injects holes among source and drain electrodes, and a composite layer containing an organic compound having an electron-transporting property and an alkaline metal or an alkaline earth metal is used as part of the electrode that injects electrons, where either composite layer has a structure of being in contact with an organic semiconductor layer.

Abstract: It is an object of the present invention to provide an organic transistor having a low drive voltage. It is also another object of the present invention to provide an organic transistor, in which light emission can be obtained, which can be manufactured simply and easily. According to an organic light-emitting transistor, a composite layer containing an organic compound having a hole-transporting property and a metal oxide is used as part of the electrode that injects holes among source and drain electrodes, and a composite layer containing an organic compound having an electron-transporting property and an alkaline metal or an alkaline earth metal is used as part of the electrode that injects electrons, where either composite layer has a structure of being in contact with an organic semiconductor layer.

Abstract: To provide a method for manufacturing a transistor which has little variation in characteristics and favorable electric characteristics. A gate insulating film is formed over a gate electrode; a semiconductor layer including a microcrystalline semiconductor is formed over the gate insulating film; an impurity semiconductor layer is formed over the semiconductor layer; a mask is formed over the impurity semiconductor layer, and then the semiconductor layer and the impurity semiconductor layer are etched with use of the mask to form a semiconductor stacked body; the mask is removed and then the semiconductor stacked body is exposed to plasma generated in an atmosphere containing a rare gas to form a barrier region on a side surface of the semiconductor stacked body; and a wiring over the impurity semiconductor layer of the semiconductor stacked body is formed.

Abstract: A method for etching is provided in which the etching selectivity of an amorphous semiconductor film to a crystalline semiconductor film is high. Part of a stacked semiconductor film in which an amorphous semiconductor film is provided on a crystalline semiconductor film is etched using a mixed gas of a Br-based gas, a F-based gas, and an oxygen gas, so that part of the crystalline semiconductor film provided in the stacked semiconductor film is exposed. Reduction in the film thickness of the exposed portion can be suppressed by performing the etching in such a manner. Moreover, when etching for forming a back channel portion of a thin film transistor is performed with the method for etching, favorable electric characteristics of the thin film transistor can be obtained. An insulating layer is preferably provided over the thin film transistor.

Abstract: It is an object to provide an organic field effect transistor including an electrode which can reduce an energy barrier at an interface between a conductive layer and a semiconductor layer, and a semiconductor device including the organic field effect transistor. A composite layer containing an organic compound and an inorganic compound is provided in at least part of one of a source electrode and a drain electrode in an organic field effect transistor, and as the organic compound, a carbazole derivative represented by the general formula (1) is used. By providing the composite layer in at least part of one of the source electrode and the drain electrode, an energy barrier at an interface between a conductive layer and a semiconductor layer can be reduced.

Abstract: It is an object to provide an organic field effect transistor including an electrode which can reduce an energy barrier at an interface between a conductive layer and a semiconductor layer, and a semiconductor device including the organic field effect transistor. A composite layer containing an organic compound and an inorganic compound is provided in at least part of one of a source electrode and a drain electrode in an organic field effect transistor, and as the organic compound, a carbazole derivative represented by the general formula (1) is used. By providing the composite layer in at least part of one of the source electrode and the drain electrode, an energy barrier at an interface between a conductive layer and a semiconductor layer can be reduced.

Abstract: It is an object of the present invention, in a case of using a conductive material as part of an electrode for an organic transistor, to provide an organic transistor having a structure whose characteristics are not controlled by the work function of the conductive material. Moreover, it is other objects of the present invention to provide an organic transistor having favorable carrier mobility and to provide an organic transistor which is excellent in durability. A composite layer containing an organic compound and an inorganic material is used for an electrode for an organic field effect transistor, that is, at least part of one of a source electrode and a drain electrode in the organic field effect transistor.

Abstract: An embodiment is a thin film transistor which includes a gate electrode layer, a gate insulating layer provided so as to cover the gate electrode layer; a first semiconductor layer entirely overlapped with the gate electrode layer; a second semiconductor layer provided over and in contact with the first semiconductor layer and having a lower carrier mobility than the first semiconductor layer; an impurity semiconductor layer provided in contact with the second semiconductor layer; a sidewall insulating layer provided so as to cover at least a sidewall of the first semiconductor layer; and a source and drain electrode layers provided in contact with at least the impurity semiconductor layer. The second semiconductor layer may consist of parts which are apart from each other over the first semiconductor layer.

Abstract: It is an object of the present invention to form an organic transistor including an organic semiconductor having high crystallinity without loosing an interface between an organic semiconductor of a channel where carriers are spread out and a gate insulating layer and deteriorating a yield. A semiconductor device according to the present invention has a stacked structure of organic semiconductor layers, and at least the upper organic semiconductor layer is in a polycrystalline or a single crystalline state and the lower organic semiconductor layer is made of a material serving as a channel. Carrier mobility can be increased owing to the upper organic semiconductor layer having high crystallinity; thus, insufficient contact due to the upper organic semiconductor layer can be compensated by the lower organic semiconductor layer.

Abstract: A nonvolatile memory has a problem in that applied voltage is high. This is because a carrier needs to be injected into a floating gate through an insulating film by a tunneling effect. In addition, there is concern about deterioration of the insulating film by performing such carrier injection. An object of the present invention is to provide a memory in which applied voltage is lowered and deterioration of an insulating film is prevented. One feature is to use a layer in which an inorganic compound having a charge-transfer complex is mixed with an organic compound as a layer functioning as a floating gate of a memory. A specific example is an element having a transistor structure where a layer in which an inorganic compound having a charge-transfer complex is mixed with an organic compound and which is sandwiched between insulating layers is used as a floating gate.