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 having favorable electrical characteristics is provided. A semiconductor device having stable electrical characteristics is provided. A highly reliable semiconductor device is provided. The semiconductor device includes a semiconductor layer, a first insulating layer, and a first conductive layer. The semiconductor layer includes an island-shaped top surface. The first insulating layer is provided in contact with a top surface and a side surface of the semiconductor layer. The first conductive layer is positioned over the first insulating layer and includes a portion overlapping with the semiconductor layer. In addition, the semiconductor layer includes a metal oxide, and the first insulating layer includes an oxide. The semiconductor layer includes a first region overlapping with the first conductive layer and a second region not overlapping with the first conductive layer. The first insulating layer includes a third region overlapping with the first conductive layer and a fourth region not overlapping with the first conductive layer. Furthermore, the second region and the fourth region contain phosphorus or boron.

The semiconductor device is manufactured through the following steps: after first heat treatment is performed on an oxide semiconductor film, the oxide semiconductor film is processed to form an oxide semiconductor layer; immediately after that, side walls of the oxide semiconductor layer are covered with an insulating oxide; and in second heat treatment, the side surfaces of the oxide semiconductor layer are prevented from being exposed to a vacuum and defects (oxygen deficiency) in the oxide semiconductor layer are reduced.

A semiconductor device having favorable electrical characteristics is provided. A first oxide is formed over a substrate; a first insulator is formed over the first oxide; an opening reaching the first oxide is formed in the first insulator; a first oxide film is deposited in contact with the first oxide and the first insulator in the opening; a first insulating film is deposited over the first oxide film; microwave treatment is performed from above the first insulating film; heat treatment is performed on one or both of the first insulating film and the first oxide; a first conductive film is deposited over the first insulating film; and part of the first oxide film, part of the first insulating film, and part of the first conductive film are removed until a top surface of the first insulator is exposed, so that a second oxide, a second insulator, and a first conductor are formed. The microwave treatment is performed using a gas containing oxygen under reduced pressure, and the heat treatment is performed under reduced pressure.

Provided is a semiconductor device A including: a first electrode 10; a second electrode 20; a semiconductor layer 30 in contact with the first electrode 10 and the second electrode 20; and a protective layer 40 configured to cover at least a part of a surface of the semiconductor layer 30, wherein the protective layer 40 includes a spinel oxide.

An oxide semiconductor crystallization method may include depositing an In—Ga—Zn oxide over the substrate while heating a substrate to a temperature of 200 to 300° C., and heat-treating the deposited In—Ga—Zn oxide at a temperature of 200 to 350° C., thereby forming an oxide semiconductor layer crystallized throughout an entire thickness thereof.

Methods for manufacturing a semiconductor structure is provided. The method for manufacturing the semiconductor structure includes forming nanowire structures over a substrate and forming a gate structure across nanowire structures. The method for manufacturing the semiconductor structure also includes forming a source/drain structure adjacent to the gate structure and forming a Si layer over the source/drain structure. The method for manufacturing the semiconductor structure also includes forming a SiGe layer over the Si layer and oxidizing the SiGe layer to form an oxide layer. The method for manufacturing the semiconductor structure also includes forming a contact through the Si layer over the source/drain structure.

Methods and apparatus for forming a thin film transistor (TFT) having a metal oxide layer. The method may include forming an amorphous metal oxide layer and treating the metal oxide layer with a silicon containing gas or plasma including Si.sup.4+ ions. The silicon treatment of the metal oxide layer helps fill the oxygen vacancies in the metal oxide channel layer, leading to a more stable TFT and preventing a negative threshold voltage in the TFT.

According to one embodiment, a thin-film transistor includes a polycrystalline semiconductor layer, a gate electrode opposing the polycrystalline semiconductor layer, a gate insulating film provided between the gate electrode and the polycrystalline semiconductor layer and in contact with the gate electrode, and an amorphous layer provided between the gate insulating film and the polycrystalline semiconductor layer, and in contact with the gate insulating film and the polycrystalline semiconductor layer.

A transistor including an oxide semiconductor, which has good on-state characteristics, and a high-performance semiconductor device including a transistor capable of high-speed response and high-speed operation. In the transistor including an oxide semiconductor, oxygen-defect-inducing factors are introduced (added) into an oxide semiconductor layer, whereby the resistance of a source and drain regions are selectively reduced. Oxygen-defect-inducing factors are introduced into the oxide semiconductor layer, whereby oxygen defects serving as donors can be effectively formed in the oxide semiconductor layer. The introduced oxygen-defect-inducing factors are one or more selected from titanium, tungsten, and molybdenum, and are introduced by an ion implantation method.