A semiconductor device having high operation frequency is provided. The semiconductor device includes a transistor including a first conductive layer, a first insulating layer, a second insulating layer, a first oxide, a second oxide, a third oxide, a third insulating layer, and a second conductive layer that are stacked in this order, and a fourth insulating layer. The first conductive layer and the second conductive layer include a region overlapping with the second oxide. In a channel width direction of the transistor, a level of the bottom surface of the second oxide is from more than or equal to −5 nm to less than 0 nm when a level of a region of the bottom surface of the second conductive layer which does not overlap with the second oxide is regarded as a reference.

This invention provides a semiconductor device with high speed operation and reduced size. A circuit includes a circuit including a memory circuit and a circuit including a logic circuit; thus, the circuit functions as a memory device having a function of storing data and a function of performing logic operation. The circuit can output, in addition to data stored in the circuit, data corresponding to a result of logic operation performed using data stored in the circuit as an input signal. The circuit can directly obtain a result of logic operation from the circuit, and thus, the frequency of input/output of a signal performed between the circuit and the circuit can be reduced.

A memory device which stores a large amount of data is provided. The memory device includes a first transistor, a second transistor, a third transistor, a first capacitor, a second capacitor, and first to third wirings. The first transistor includes an oxide semiconductor in a channel formation region, the second transistor includes silicon in a channel formation region, and the third transistor includes silicon in a channel formation region. The first capacitor is provided in the same layer as the first transistor. A region of the second capacitor and a region of the first capacitor overlap with each other. The thickness of a dielectric of the second capacitor is preferably larger than the thickness of a dielectric of the first capacitor.

A memory device that is as small in area as possible and has an extremely long data retention period. A transistor with extremely low leakage current is used as a cell transistor of a memory element in a memory device. Moreover, in order to reduce the area of a memory cell, the transistor is formed so that its source and drain are stacked in the vertical direction in a region where a bit line and a word line intersect each other. Further, a capacitor is stacked above the transistor.

To provide a transistor formed using an oxide semiconductor film with reduced oxygen vacancies. To provide a semiconductor device that operates at high speed. To provide a highly reliable semiconductor device. To provide a miniaturized semiconductor device. The semiconductor device includes an oxide semiconductor film; a gate electrode overlapping with the oxide semiconductor film; a gate insulating film between the oxide semiconductor film and the gate electrode; and a protective insulating film that is above the oxide semiconductor film, the gate electrode, and the gate insulating film and includes a region containing phosphorus or boron.

A conventional DRAM needs to be refreshed at an interval of several tens of milliseconds to hold data, which results in large power consumption. In addition, a transistor therein is frequently turned on and off; thus, deterioration of the transistor is also a problem. These problems become significant as the memory capacity increases and transistor miniaturization advances. A transistor is provided which includes a wide-gap semiconductor and has a trench structure including a trench for a gate electrode and a trench for element isolation. Even when the distance between a source electrode and a drain electrode is decreased, the occurrence of a short-channel effect can be suppressed by setting the depth of the trench for the gate electrode as appropriate.

A semiconductor device includes an oxide layer, a source electrode layer in contact with the oxide layer, a first drain electrode layer in contact with the oxide layer, a second drain electrode layer in contact with the oxide layer, a gate insulating film in contact with the oxide layer, a first gate electrode layer overlapping with the source electrode layer and the first drain electrode layer and overlapping with a top surface of the oxide layer with the gate insulating film interposed therebetween, a second gate electrode layer overlapping with the source electrode layer and the second drain electrode layer and overlapping with the top surface of the oxide layer with the gate insulating film interposed therebetween, and a third gate electrode layer overlapping with a side surface of the oxide layer with the gate insulating film interposed therebetween.

A semiconductor device with less variation in transistor characteristics is provided. The semiconductor device includes a semiconductor film, a pair of blocking films over the semiconductor film, and an insulating film provided over the semiconductor film and between the pair of blocking films. The semiconductor film includes a pair of n-type regions and an i-type region provided between the pair of n-type regions. The n-type regions overlap with the blocking films. The i-type region overlaps with the insulating film.

A novel metal oxide is provided. The metal oxide includes a crystal. The crystal has a structure in which a first layer, a second layer, and a third layer are stacked. The first layer, the second layer, and the third layer are each substantially parallel to a formation surface of the metal oxide. The first layer includes a first metal and oxygen. The second layer includes a second metal and oxygen. The third layer includes a third metal and oxygen. The first layer has an octahedral structure. The second layer has a trigonal bipyramidal structure or a tetrahedral structure. The third layer has a trigonal bipyramidal structure or a tetrahedral structure. The octahedral structure of the first layer includes an atom of the first metal at a center. The trigonal bipyramidal structure or the tetrahedral structure of the second layer includes an atom of the second metal at a center. The trigonal bipyramidal structure or the tetrahedral structure of the third layer includes an atom of the third metal at a center. The valence of the first metal is equal to the valence of the second metal. The valence of the first metal is different from the valence of the third metal.

A semiconductor device with high reliability is provided. A first conductor and a second conductor are provided over and in contact with a first oxide. A first insulator is provided to cover the first oxide, a first conductor, and a second conductor. The first insulator includes an opening portion. The first oxide is exposed on a bottom surface of the opening portion. A side surface of the first conductor and a side surface of the second conductor are exposed on a side surface of the opening portion. A second oxide is provided in contact with the first oxide, the side surface of the first conductor, and the second conductor in the opening portion. A second insulator is provided in the opening portion with the second oxide therebetween. A third conductor is provided in the opening portion with the second insulator therebetween. Lower end portions of the side surface of the first conductor and the second conductor touch an ellipse or a circle with a center above the first oxide.