The purpose of the invention is to form the TFT of the oxide semiconductor, in which influence of variation in mask alignment is suppressed, thus, manufacturing a display device having a TFT of stable characteristics. The concrete measure is as follows. A display device including plural pixels, each of the plural pixels having a thin film transistor (TFT) of an oxide semiconductor comprising: a width of the oxide semiconductor in the channel width direction is wider than a width of the gate electrode in the channel width direction.

The purpose of the invention is to form the TFT of the oxide semiconductor, in which influence of variation in mask alignment is suppressed, thus, manufacturing a display device having a TFT of stable characteristics. The concrete measure is as follows. A display device including plural pixels, each of the plural pixels having a thin film transistor (TFT) of an oxide semiconductor comprising: a width of the oxide semiconductor in the channel width direction is wider than a width of the gate electrode in the channel width direction.

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.

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.

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.

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.

A method includes placing a semiconductor substrate in a deposition chamber, wherein the semiconductor substrate includes a trench, and performing an atomic layer deposition (ALD) process to deposit a dielectric material within the trench, including flowing a first precursor of the dielectric material into the deposition chamber as a gas phase; flowing a second precursor of the dielectric material into the deposition chamber as a gas phase; and controlling the pressure and temperature within the deposition chamber such that the second precursor condenses on surfaces within the trench as a liquid phase of the second precursor, wherein the liquid phase of the second precursor has capillarity.

A semiconductor device using an oxide semiconductor is provided with stable electric characteristics to improve the reliability. In a manufacturing process of a transistor including an oxide semiconductor film, an oxide semiconductor film containing a crystal having a c-axis which is substantially perpendicular to a top surface thereof (also called a first crystalline oxide semiconductor film) is formed; oxygen is added to the oxide semiconductor film to amorphize at least part of the oxide semiconductor film, so that an amorphous oxide semiconductor film containing an excess of oxygen is formed; an aluminum oxide film is formed over the amorphous oxide semiconductor film; and heat treatment is performed thereon to crystallize at least part of the amorphous oxide semiconductor film, so that an oxide semiconductor film containing a crystal having a c-axis which is substantially perpendicular to a top surface thereof (also called a second crystalline oxide semiconductor film) is formed.

A semiconductor device using an oxide semiconductor is provided with stable electric characteristics to improve the reliability. In a manufacturing process of a transistor including an oxide semiconductor film, an oxide semiconductor film containing a crystal having a c-axis which is substantially perpendicular to a top surface thereof (also called a first crystalline oxide semiconductor film) is formed; oxygen is added to the oxide semiconductor film to amorphize at least part of the oxide semiconductor film, so that an amorphous oxide semiconductor film containing an excess of oxygen is formed; an aluminum oxide film is formed over the amorphous oxide semiconductor film; and heat treatment is performed thereon to crystallize at least part of the amorphous oxide semiconductor film, so that an oxide semiconductor film containing a crystal having a c-axis which is substantially perpendicular to a top surface thereof (also called a second crystalline oxide semiconductor film) is formed.

An array substrate according to the present invention is a TFT substrate including a pixel TFT and a drive TFT on a substrate, where the pixel TFT includes a first source electrode, a first drain electrode, and an amorphous silicon layer, and the drive TFT includes a third oxide semiconductor layer provided on a gate insulating film while overlapping a second gate electrode in plan view, and a second source electrode and a second drain electrode overlapping the third oxide semiconductor layer in plan view, with a third separation portion separating the second source electrode and the second drain electrode from each other.