A method of manufacturing an array substrate is discussed. The method includes forming a gate line on a substrate including a pixel region, forming a gate electrode on the substrate and connected to the gate line, and forming a gate insulating layer on the gate line and the gate electrode. The method further includes forming a data line on the gate insulating layer and crossing the gate line to define the pixel region, forming a source electrode and a drain electrode on the gate insulating layer and corresponding to the gate electrode, the source electrode connected to the data line and the drain electrode spaced apart from the source electrode, and forming an oxide semiconductor layer on top of the source and drain electrodes.

The invention provides an oxide semiconductor layer that has less cracks and is excellent in electrical property and stability, as well as a semiconductor element and an electronic device each including the oxide semiconductor layer. The invention provides an exemplary method of producing an oxide semiconductor layer, and the method includes the precursor layer forming step of forming, on or above a substrate, a layered oxide semiconductor precursor including a compound of metal to be oxidized into an oxide semiconductor dispersed in a solution including a binder made of aliphatic polycarbonate, and the annealing step of heating the precursor layer at a first temperature achieving decomposition of 90 wt % or more of the binder, and then annealing the precursor layer at a temperature equal to or higher than a second temperature (denoted by X) that is higher than the first temperature, achieves bonding between the metal and oxygen, and has an exothermic peak value in differential thermal analysis (DTA).

An array substrate for a liquid crystal display device includes a substrate; a semiconductor layer on the substrate; a gate electrode on the semiconductor layer; source and drain electrodes that are on and contact the semiconductor layer; and an oxide layer that corresponds to the semiconductor layer and is on the gate electrode.

An oxide semiconductor film includes indium (In), cerium (Ce), zinc (Zn) and oxygen (O) elements, and a molar ratio of the In, Ce, and Zn as In:Ce:Zn is in a range of 2:1:(0.5 to 2). A method for making a oxide semiconductor film includes a step of forming an oxide film on a substrate by using a sputtering method and a sputtering target comprising In.sub.2CeZn.sub.xO.sub.5+x, wherein x=0.52.

A semiconductor device for high power application in which a novel semiconductor material having high mass productivity is provided. An oxide semiconductor film is formed, and then, first heat treatment is performed on the exposed oxide semiconductor film in order to reduce impurities such as moisture or hydrogen in the oxide semiconductor film. Next, in order to further reduce impurities such as moisture or hydrogen in the oxide semiconductor film, oxygen is added to the oxide semiconductor film by an ion implantation method, an ion doping method, or the like, and after that, second heat treatment is performed on the exposed oxide semiconductor film.

A change in electrical characteristics is suppressed and reliability in a semiconductor device using a transistor including an oxide semiconductor is improved. Oxygen is introduced into a surface of an insulating film, and then, an oxide semiconductor, a layer which is capable of blocking oxygen, a gate insulating film, and other films which composes a transistor are formed. For at least one of the first gate insulating film and the insulating film, three signals in Electron Spin Resonance Measurement are each observed in a certain range of g-factor. Reducing the sum of the spin densities of the signals will improve reliability of the semiconductor device.

An object is to provide a display device which operates stably with use of a transistor having stable electric characteristics. In manufacture of a display device using transistors in which an oxide semiconductor layer is used for a channel formation region, a gate electrode is further provided over at least a transistor which is applied to a driver circuit. In manufacture of a transistor in which an oxide semiconductor layer is used for a channel formation region, the oxide semiconductor layer is subjected to heat treatment so as to be dehydrated or dehydrogenated; thus, impurities such as moisture existing in an interface between the oxide semiconductor layer and the gate insulating layer provided below and in contact with the oxide semiconductor layer and an interface between the oxide semiconductor layer and a protective insulating layer provided on and in contact with the oxide semiconductor layer can be reduced.

When a transistor having bottom gate bottom contact structure is manufactured, for example, a conductive layer constituting a source and a drain has a three-layer structure and two-step etching is performed. In the first etching process, an etching method in which the etching rates for at least the second film and the third film are high is employed, and the first etching process is performed until at least the first film is exposed. In the second etching process, an etching method in which the etching rate for the first film is higher than that in the first etching process and the etching rate for a layer provided below and in contact with the first film is lower than that in the first etching process is employed. The side wall of the second film is slightly etched when a resist mask is removed after the second etching process.

A semiconductor device having a structure which can prevent a decrease in electrical characteristics due to miniaturization is provided. The semiconductor device includes, over an insulating surface, a stack in which a first oxide semiconductor layer and a second oxide semiconductor layer are sequentially formed, and a third oxide semiconductor layer covering part of a surface of the stack. The third oxide semiconductor layer includes a first layer in contact with the stack and a second layer over the first layer. The first layer includes a microcrystalline layer, and the second layer includes a crystalline layer in which c-axes are aligned in a direction perpendicular to a surface of the first layer.

The transistor includes a gate electrode, a gate insulating film over the gate electrode, an oxide semiconductor film over the gate insulating film, a source electrode and a drain electrode electrically connected to the oxide semiconductor film. The oxide semiconductor film includes a first oxide semiconductor film on the gate electrode side and a second oxide semiconductor film over the first oxide semiconductor film. The first oxide semiconductor film includes a first region in which an atomic proportion of In is larger than that of M (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf). The second oxide semiconductor film includes a second region in which an atomic proportion of In is smaller than that of the first oxide semiconductor film. The second region includes a portion thinner than the first region.