A thin film transistor includes a gate electrode, an active layer formed of oxide semiconductor material on a substrate, and a gate insulation layer therebetween. The active layer includes a channel region corresponding to the gate electrode, a source region at one side of the channel region, and a drain region at the other side of the channel region. The source region includes a first upper portion and the drain region includes a second upper portion that includes the oxide semiconductor material and Si.

A thin film transistor includes a gate electrode, an active layer formed of oxide semiconductor material on a substrate, and a gate insulation layer therebetween. The active layer includes a channel region corresponding to the gate electrode, a source region at one side of the channel region, and a drain region at the other side of the channel region. The source region includes a first upper portion and the drain region includes a second upper portion that includes the oxide semiconductor material and Si.

A method includes forming a fin extending from a substrate; forming an first isolation region along opposing sidewalls of the fin; forming a gate structure over the fin; forming an epitaxial source/drain region in the fin adjacent the gate structure; forming an etch stop layer over the epitaxial source/drain region and over the gate structure; forming a protection layer over the etch stop layer, the protection layer including silicon oxynitride; and forming a second isolation material over the protection layer, wherein forming the second isolation material reduces a nitrogen concentration of the protection layer.

A minute transistor is provided. A transistor with low parasitic capacitance is provided. A transistor having high frequency characteristics is provided. A semiconductor device including the transistor is provided. A semiconductor device includes an oxide semiconductor, a first conductor, a second conductor, a third conductor, a first insulator, and a second insulator. The first conductor overlaps with the oxide semiconductor with the first insulator positioned therebetween. The second insulator has an opening and a side surface of the second insulator overlaps with a side surface of the first conductor in the opening with the first insulator positioned therebetween. Part of a surface of the second conductor and part of a surface of the third conductor are in contact with the first insulator in the opening. The oxide semiconductor overlaps with the second conductor and the third conductor.

A minute transistor is provided. A transistor with low parasitic capacitance is provided. A transistor having high frequency characteristics is provided. A semiconductor device including the transistor is provided. A semiconductor device includes an oxide semiconductor, a first conductor, a second conductor, a third conductor, a first insulator, and a second insulator. The first conductor overlaps with the oxide semiconductor with the first insulator positioned therebetween. The second insulator has an opening and a side surface of the second insulator overlaps with a side surface of the first conductor in the opening with the first insulator positioned therebetween. Part of a surface of the second conductor and part of a surface of the third conductor are in contact with the first insulator in the opening. The oxide semiconductor overlaps with the second conductor and the third conductor.

In a transistor including an oxide semiconductor layer, an oxide insulating layer is formed so as to be in contact with the oxide semiconductor layer. Then, oxygen is introduced (added) to the oxide semiconductor layer through the oxide insulating layer, and heat treatment is performed. Through these steps of oxygen introduction and heat treatment, impurities such as hydrogen, moisture, a hydroxyl group, or hydride are intentionally removed from the oxide semiconductor layer, so that the oxide semiconductor layer is highly purified.

In a transistor including an oxide semiconductor layer, an oxide insulating layer is formed so as to be in contact with the oxide semiconductor layer. Then, oxygen is introduced (added) to the oxide semiconductor layer through the oxide insulating layer, and heat treatment is performed. Through these steps of oxygen introduction and heat treatment, impurities such as hydrogen, moisture, a hydroxyl group, or hydride are intentionally removed from the oxide semiconductor layer, so that the oxide semiconductor layer is highly purified.

A method of selectively forming a film on a substrate includes: a preparation process of preparing a substrate having a surface to which a metal film and an insulating film are exposed; a first removal process of removing a natural oxide film on the metal film; a first film forming process of forming a self-assembled monolayer, which suppresses formation of a titanium nitride film, on the insulating film by providing the substrate with a compound for forming the self-assembled monolayer, the compound having a functional group containing fluorine and carbon; a second film forming process of forming a titanium nitride film on the metal film; an oxidation process of oxidizing the surface of the substrate; and a second removal process of removing a titanium oxide film, which is formed on the metal film and the self-assembled monolayer, by providing the surface of the substrate with the compound.

In a semiconductor device including a transistor including an oxide semiconductor film and a protective film over the transistor, an oxide insulating film containing oxygen in excess of the stoichiometric composition is formed as the protective film under the following conditions: a substrate placed in a treatment chamber evacuated to a vacuum level is held at a temperature higher than or equal to 180° C. and lower than or equal to 260° C.; a source gas is introduced into the treatment chamber so that the pressure in the treatment chamber is set to be higher than or equal to 100 Pa and lower than or equal to 250 Pa; and a high-frequency power higher than or equal to 0.17 W/cm.sup.2 and lower than or equal to 0.5 W/cm.sup.2 is supplied to an electrode provided in the treatment chamber.

In a semiconductor device including a transistor including an oxide semiconductor film and a protective film over the transistor, an oxide insulating film containing oxygen in excess of the stoichiometric composition is formed as the protective film under the following conditions: a substrate placed in a treatment chamber evacuated to a vacuum level is held at a temperature higher than or equal to 180° C. and lower than or equal to 260° C.; a source gas is introduced into the treatment chamber so that the pressure in the treatment chamber is set to be higher than or equal to 100 Pa and lower than or equal to 250 Pa; and a high-frequency power higher than or equal to 0.17 W/cm.sup.2 and lower than or equal to 0.5 W/cm.sup.2 is supplied to an electrode provided in the treatment chamber.