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 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 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.

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.

A p-type oxide which is amorphous and is represented by the following compositional formula: xAO.yCu.sub.2O where x denotes a proportion by mole of AO and y denotes a proportion by mole of Cu.sub.2O and x and y satisfy the following expressions: 0x<100 and x+y=100, and A is any one of Mg, Ca, Sr and Ba, or a mixture containing at least one selected from the group consisting of Mg, Ca, Sr and Ba.

A display substrate includes a base substrate comprising a plurality of sub-pixels, a first switching element disposed on the base substrate and electrically connected to a gate line extending in a first direction and a data line extending in a second direction crossing the first direction, a color filter layer disposed on the switching element and comprising a red color filter, a green color filter, a blue color filter and a white color filter alternately disposed on the plurality of sub-pixels, respectively, a column spacer disposed on the color filter and comprising the same material as that of the white color filter, an insulation layer disposed on the color filter and the column spacer and a pixel electrode disposed on the insulation layer.

An object is to manufacture a highly reliable semiconductor device including a thin film transistor with stable electric characteristics. In a method for manufacturing a semiconductor device including a thin film transistor in which an oxide semiconductor film is used for a semiconductor layer including a channel formation region, heat treatment (for dehydration or dehydrogenation) is performed to improve the purity of the oxide semiconductor film and reduce impurities including moisture or the like. After that, slow cooling is performed under an oxygen atmosphere. Besides impurities including moisture or the like exiting in the oxide semiconductor film, heat treatment causes reduction of impurities including moisture or the like exiting in a gate insulating layer and those in interfaces between the oxide semiconductor film and films which are provided over and below the oxide semiconductor and in contact therewith.

A substrate including gate wirings including gate line and a gate electrode disposed on the substrate, a storage line disposed on the same layer as the gate wirings, a gate insulating layer disposed on the gate wirings and the storage line, an oxide semiconductor layer pattern disposed on the gate insulating layer, data wirings including a data line crossing the gate line, a source electrode disposed on one side of the oxide semiconductor layer pattern, and a drain electrode disposed on another side of the oxide semiconductor layer, and an etch stopper including a first etch stopper portion disposed between the storage line and the data line and partially overlapping both the data line and the storage line.

The present invention provides a thin-film transistor in which transistor characteristics such as drain current and threshold voltage are improved, and a method of manufacturing the same. The present invention provides a thin-film transistor provided with a source electrode (108), a drain electrode (109), a semiconductor layer (105), a gate electrode (103), and an insulating layer (104); wherein the semiconductor layer (105) contains a composite metal oxide obtained by adding to a first metal oxide an oxide having an oxygen dissociation energy that is at least 200 kJ/mol greater than the oxygen dissociation energy of the first metal oxide, whereby the amount of oxygen vacancy is controlled; and the insulating layer (104) is provided with an SiO.sub.2 layer, a high-permittivity first layer, and a high-permittivity second layer, whereby the dipoles generated at the boundary between the SiO.sub.2 layer and the high-permittivity layers are used to control the threshold voltage.

A semiconductor device includes an oxide semiconductor layer including a crystalline region over an insulating surface, a source electrode layer and a drain electrode layer in contact with the oxide semiconductor layer, a gate insulating layer covering the oxide semiconductor layer, the source electrode layer, and the drain electrode layer, and a gate electrode layer over the gate insulating layer in a region overlapping with the crystalline region. The crystalline region includes a crystal whose c-axis is aligned in a direction substantially perpendicular to a surface of the oxide semiconductor layer.