A minute transistor is provided that includes a first insulator, a second insulator, a first, conductor, a second conductor, and third conductor, in which an angle is formed between a side surface of the first insulator and a top surface of the first conductor, and a length between the first conductor and a surface of the second conductor closest to the first conductor is at least greater than a length between the first conductor and the third conductor.

A semiconductor device with a large storage capacity per unit area is provided.

A semiconductor device includes a memory cell. The memory cell includes a first conductor; a first insulator over the first conductor; a first oxide over the first insulator and including a first region, a second region, and a third region positioned between the first region and the second region; a second insulator over the first oxide; a second conductor over the second insulator; a third insulator positioned in contact with a side surface of the first region; and a second oxide positioned on the side surface of the first region, with the third insulator therebetween. The first region includes a region overlapping the first conductor. The third region includes a region overlapped by the second conductor. The first region and the second region have a lower resistance than the third region.

A memory device occupying a small area is provided. In a memory cell including a reading transistor, a writing transistor, and a capacitor, the writing transistor is provided above the reading transistor. Alternatively, the reading transistor is provided above the writing transistor. An oxide semiconductor is used for a semiconductor layer where a channel of the writing transistor is formed. An oxide semiconductor is used for a semiconductor layer where a channel of the reading transistor is formed. Memory cells are arranged in a matrix.

A semiconductor device with 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, a second insulating layer, and a conductive layer. The first insulating layer is in contact with part of the top surface of the semiconductor layer, the conductive layer is positioned over the first insulating layer, and the second insulating layer is positioned over the semiconductor layer. The semiconductor layer contains a metal oxide and includes a first region overlapping with the conductive layer and a second region not overlapping with the conductive layer. The second region is in contact with the second insulating layer. The second insulating layer contains oxygen and a first element. The first element is one or more of phosphorus, boron, magnesium, aluminum, and silicon.

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.

A semiconductor device having high reliability is provided. The semiconductor device includes a transistor and an insulator placed so as to surround the transistor; the insulator has a barrier property against hydrogen; the transistor includes an oxide and a conductor; the conductor includes nitrogen and a metal; the conductor has a physical property of extracting hydrogen; the conductor includes a region having a hydrogen concentration higher than or equal to 2.0×10.sup.19 atoms/cm.sup.3 and lower than or equal to 1.0×10.sup.21 atoms/cm.sup.3; and at least part of hydrogen atoms included in the region is bonded to a nitrogen atom.

A miniaturized transistor having excellent electrical characteristics is provided with high yield. Further, a semiconductor device including the transistor and having high performance and high reliability is manufactured with high productivity. In a semiconductor device including a transistor in which an oxide semiconductor film including a channel formation region and low-resistance regions between which the channel formation region is sandwiched, a gate insulating film, and a gate electrode layer whose top surface and side surface are covered with an insulating film including an aluminum oxide film are stacked, a source electrode layer and a drain electrode layer are in contact with part of the oxide semiconductor film and the top surface and a side surface of the insulating film including an aluminum oxide film.

An object of one embodiment of the present invention is to provide a semiconductor device with a novel structure in which stored data can be stored even when power is not supplied in a data storing time and there is no limitation on the number of times of writing. The semiconductor device includes a first transistor which includes a first channel formation region using a semiconductor material other than an oxide semiconductor, a second transistor which includes a second channel formation region using an oxide semiconductor material, and a capacitor. One of a second source electrode and a second drain electrode of the second transistor is electrically connected to one electrode of the capacitor.

A semiconductor device with a small variation in transistor characteristics is provided. The semiconductor device includes an oxide semiconductor, a first conductor and a second conductor over the oxide semiconductor, a first insulator in contact with a top surface of the first conductor, a second insulator in contact with a top surface of the second conductor, a third insulator which is positioned over the first insulator and the second insulator and has an opening overlapping with a region between the first conductor and the second conductor, a fourth insulator positioned over the oxide semiconductor and in the region between the first conductor and the second conductor, and a third conductor over the fourth insulator. Each of the first insulator and the second insulator is a metal oxide including an amorphous structure.

To provide a semiconductor device that holds data even when power supply is stopped. The semiconductor device includes a first transistor, a second transistor, a third transistor, and a capacitor. One of a source electrode and a drain electrode of the first transistor is electrically connected to one of a source electrode and a drain electrode of the third transistor and one electrode of the capacitor. A gate electrode of the second transistor is electrically connected to the other of the source electrode and the drain electrode of the third transistor.