It is an object to manufacture a semiconductor device in which a transistor including an oxide semiconductor has normally-off characteristics, small fluctuation in electric characteristics, and high reliability. First, first heat treatment is performed on a substrate, a base insulating layer is formed over the substrate, an oxide semiconductor layer is formed over the base insulating layer, and the step of performing the first heat treatment to the step of forming the oxide semiconductor layer are performed without exposure to the air. Next, after the oxide semiconductor layer is formed, second heat treatment is performed. An insulating layer from which oxygen is released by heating is used as the base insulating layer.

A manufacturing method of a TFT substrate structure is provided, in which a graphene layer is formed on a semiconductor layer and after the formation of a second metal layer, the second metal layer is used as a shielding mask to conduct injection of fluoride ions into the graphene layer to form a modified area in a portion of the graphene layer that is located on and corresponds to a channel zone of the semiconductor layer. The modified area of the graphene layer shows a property of electrical insulation and a property of blocking moisture/oxygen so as to provide protection to the channel zone. Portions of the graphene layer that are located under source and drain electrodes are not doped with ions and preserve the excellent electrical conduction property of graphene to provide electrical connection between the source and drain electrodes and the semiconductor layer.

An array substrate and a display device are provided. A gate insulating layer and a gate electrode are formed on a semiconductor layer in sequence, the gate insulating layer and the gate electrode are located in a middle position of the semiconductor layer and have a uniform shape and size. In a region on the semiconductor layer that is not covered by the gate insulating layer, there is further provided a metal diffusion layer. A barrier layer includes a portion covering the gate insulating layer and the gate electrode and a portion located around the semiconductor layer. A passivation layer covers the semiconductor layer, the gate insulating layer, the gate electrode and the barrier layer. Source and drain electrodes are connected to the metal diffusion layer respectively, and a pixel electrode contacts with the drain electrode.

A method including providing a substrate with a gate, a layer of gate insulator material adjacent the gate, and a layer of metal oxide semiconductor material positioned on the gate insulator opposite the gate, forming a selectively patterned etch stop passivation layer and heating at elevated temperature in an oxygen-containing or nitrogen-containing or inert ambience to selectively increase the carrier concentration in regions of the metal oxide semiconductor not covered by the etch stop layer, on which overlying and spaced apart source/drain metals are formed. Subsequently heating the transistor in an oxygen-containing or nitrogen-containing or inert ambience to further improve the source/drain contacts and adjust the threshold voltage to a desired level. Providing additional passivation layer(s) on top of the transistor with electric insulation and barrier property to moisture and chemicals in the surrounding environment.

An object is to reduce to reduce variation in threshold voltage to stabilize electric characteristics of thin film transistors each using an oxide semiconductor layer. An object is to reduce an off current. The thin film transistor using an oxide semiconductor layer is formed by stacking an oxide semiconductor layer containing insulating oxide over the oxide semiconductor layer so that the oxide semiconductor layer and source and drain electrode layers are in contact with each other with the oxide semiconductor layer containing insulating oxide interposed therebetween; whereby, variation in threshold voltage of the thin film transistors can be reduced and thus the electric characteristics can be stabilized. Further, an off current can be reduced.

A semiconductor device including a transistor is provided. The transistor includes a gate electrode, a first insulating film over the gate electrode, a second insulating film over the first insulating film, an oxide semiconductor film over the second insulating film, a source electrode and a drain electrode electrically connected to the oxide semiconductor film, a third insulating film over the source electrode, and a fourth insulating film over the drain electrode. A fifth insulating film including oxygen is provided over the transistor. The third insulating film includes a first portion, the fourth insulating film includes a second portion, and the fifth insulating film includes a third portion. The amount of oxygen molecules released from each of the first portion and the second portion is smaller than the amount of oxygen molecules released from the third portion when the amounts are measured by thermal desorption spectroscopy.

An oxide semiconductor device and a method for manufacturing the same are provided in the present invention. The oxide semiconductor device includes a back gate, an oxide semiconductor film, a pair of source and drain electrodes, agate insulating film, a gate electrode on the oxide semiconductor film with the gate insulating film therebetween, an insulating layer covering only over the gate electrode and the pair of source and drain electrodes, and a top blocking film over the insulating layer.

A gate electrode, a first insulating film thereover, an oxide semiconductor film thereover, a source electrode and a drain electrode thereover, and a second insulating film thereover are included. The source and the drain electrodes each include a first conductive film, a second conductive film over and in contact with the first conductive film, and a third conductive film over and in contact with the second conductive film. The second conductive film includes copper. The first and the third conductive films each include an oxide conductive film. An end portion of the first conductive film includes a region located outward from an end portion of the second conductive film. The third conductive film covers a top surface and a side surface of the second conductive film and includes a region in contact with the first conductive film.

Functionalized films are provided comprising a film of ZnO or ZnO alloy disposed over a supporting substrate and a layer of organic molecules comprising terminal carboxylic acid linkage groups, wherein the organic molecules are bound to a surface of the film of ZnO or ZnO alloy via the terminal carboxylic acid linkage groups. Thin film transistors comprising the functionalized films are also provided. The functionalized films may be formed using polycrystalline ZnO and saturated fatty acids, such as stearic acid.

Electrical characteristics of a semiconductor device including the oxide semiconductor are improved. Furthermore, a highly reliable transistor with small variation in electrical characteristics is manufactured. An oxynitride insulating film functioning as a base insulating film and a transistor in contact with the oxynitride insulating film are provided. The transistor includes an oxide semiconductor film in contact with the oxynitride insulating film functioning as a base insulating film. The total amount of gas having a mass-to-charge ratio of 30 released from the oxynitride insulating film by heat treatment and double of the amount of a gas having a mass-to-charge ratio of 32 released from the oxynitride insulating film by heat treatment is greater than or equal to 510.sup.15/cm.sup.2 and less than or equal to 510.sup.16/cm.sup.2, or greater than or equal to 510.sup.15/cm.sup.2 and less than or equal to 310.sup.16/cm.sup.2.