A novel metal oxide or a novel sputtering target is provided. A sputtering target includes a conductive material and an insulating material. The insulating material includes an oxide, a nitride, or an oxynitride including an element M1. The element M1 is one or more kinds of elements selected from Al, Ga, Si, Mg, Zr, Be, and B. The conductive material includes an oxide, a nitride, or an oxynitride including indium and zinc. A metal oxide film is deposited using the sputtering target in which the conductive material and the insulating material are separated from each other.

An object is to provide a display device which operates stably with use of a transistor having stable electric characteristics. In manufacture of a display device using transistors in which an oxide semiconductor layer is used for a channel formation region, a gate electrode is further provided over at least a transistor which is applied to a driver circuit. In manufacture of a transistor in which an oxide semiconductor layer is used for a channel formation region, the oxide semiconductor layer is subjected to heat treatment so as to be dehydrated or dehydrogenated; thus, impurities such as moisture existing in an interface between the oxide semiconductor layer and the gate insulating layer provided below and in contact with the oxide semiconductor layer and an interface between the oxide semiconductor layer and a protective insulating layer provided on and in contact with the oxide semiconductor layer can be reduced.

A silicon carbide crystal includes a seed layer, a bulk layer, and a stress buffering structure formed between the seed layer and the bulk layer. The seed layer, the bulk layer, and the stress buffering structure are each formed with a dopant that cycles between high and low dopant concentration. The stress buffering structure includes a plurality of stacked buffer layers and a transition layer over the buffer layers. The buffer layer closest to the seed layer has the same variation trend of the dopant concentration as the buffer layer closest to the transition layer, and the dopant concentration of the transition layer is equal to the dopant concentration of the seed layer.

It is an object to provide a highly reliable semiconductor device including a thin film transistor with stable electric characteristics. In a semiconductor device including an inverted staggered thin film transistor whose semiconductor layer is an oxide semiconductor layer, a buffer layer is provided over the oxide semiconductor layer. The buffer layer is in contact with a channel formation region of the semiconductor layer and source and drain electrode layers. A film of the buffer layer has resistance distribution. A region provided over the channel formation region of the semiconductor layer has lower electrical conductivity than the channel formation region of the semiconductor layer, and a region in contact with the source and drain electrode layers has higher electrical conductivity than the channel formation region of the semiconductor layer.

An object of the present invention is to provide a novel SiC single crystal with reduced internal stress while suppressing SiC sublimation. In order to solve the above problems, the present invention provides a method for producing SiC single crystals, including a stress reduction step of heating a SiC single crystal at 1800° C. or higher in an atmosphere containing Si and C elements to reduce internal stress in the SiC single crystal. With this configuration, the present invention can provide a novel SiC single crystal with reduced internal stress while suppressing SiC sublimation.

A semiconductor device with a small variation in characteristics is provided. The semiconductor device includes a first insulator; a second insulator having an opening over the first insulator; a third insulator that has a first depressed portion and is provided inside the opening; a first oxide that has a second depressed portion and is provided inside the first depressed portion; a second oxide provided inside the second depressed portion; a first conductor and a second conductor that are electrically connected to the second oxide and are apart from each other; a fourth insulator over the second oxide; and a third conductor including a region overlapping with the second oxide with the fourth insulator therebetween. The second oxide includes a first region, a second region, and a third region sandwiched between the first region and the second region in a top view. The first conductor includes a region overlapping with the first region and the second insulator. The second conductor includes a region overlapping with the second region and the second insulator. The third conductor includes a region overlapping with the third region.

A semiconductor device includes a plurality of column portions including a semiconductor. The plurality of column portions each includes a source region, a drain region, and a channel formation region including a channel formed between the source region and the drain region. The semiconductor device further includes a gate electrode provided, via an insulating layer, at a side wall of the channel formation region, and also includes a first semiconductor layer provided at a side wall of the drain region. A conductive type of the first semiconductor layer differs from a conductive type of the semiconductor included in the drain region.

A compound semiconductor has a high electron concentration of 5×10.sup.19 cm.sup.−3 or higher, exhibits an electron mobility of 46 cm.sup.2/V.Math.s or higher, and exhibits a low electric resistance, and thus is usable to produce a high performance semiconductor device. The present invention provides a group 13 nitride semiconductor of n-type conductivity that may be formed as a film on a substrate having a large area size at a temperature of room temperature to 700° C.

This disclosure relates to methods of growing crystalline layers on amorphous substrates by way of an ultra-thin seed layer, methods for preparing the seed layer, and compositions comprising both. In an aspect of the invention, the crystalline layers can be thin films. In a preferred embodiment, these thin films can be free-standing.

By using a conductive layer including Cu as a long lead wiring, increase in wiring resistance is suppressed. Further, the conductive layer including Cu is provided in such a manner that it does not overlap with the oxide semiconductor layer in which a channel region of a TFT is formed, and is surrounded by insulating layers including silicon nitride, whereby diffusion of Cu can be prevented; thus, a highly reliable semiconductor device can be manufactured. Specifically, a display device which is one embodiment of a semiconductor device can have high display quality and operate stably even when the size or definition thereof is increased.