A method for manufacturing a field effect transistor including a gate-insulating layer, an active layer, and a passivation layer. The method includes a first process of forming the gate-insulating layer; and a second process of forming the passivation layer. At least one of the first process and the second process includes: forming a first oxide containing an alkaline earth metal and at least one of gallium, scandium, yttrium, and a lanthanoid; and etching the first oxide by use of a first solution containing at least one of hydrochloric, acid, oxalic acid, nitric acid, phosphoric acid, acetic acid, sulfuric acid, and hydrogen peroxide water.

An object is to provide a semiconductor device including a semiconductor element which has favorable characteristics. A manufacturing method of the present invention includes the steps of: forming a first conductive layer which functions as a gate electrode over a substrate; forming a first insulating layer to cover the first conductive layer; forming a semiconductor layer over the first insulating layer so that part of the semiconductor layer overlaps with the first conductive layer; forming a second conductive layer to be electrically connected to the semiconductor layer; forming a second insulating layer to cover the semiconductor layer and the second conductive layer; forming a third conductive layer to be electrically connected to the second conductive layer; performing first heat treatment after forming the semiconductor layer and before forming the second insulating layer; and performing second heat treatment after forming the second insulating layer.

It is an object to provide a manufacturing method of a structure of a thin film transistor including an oxide semiconductor film, in which threshold voltage at which a channel is formed is positive and as close to 0 V as possible. A protective insulating layer is formed to cover a thin film transistor including an oxide semiconductor layer that is dehydrated or dehydrogenated by first heat treatment, and second heat treatment at a temperature that is lower than that of the first heat treatment, in which the increase and decrease in temperature are repeated plural times, is performed, whereby a thin film transistor including an oxide semiconductor layer, in which threshold voltage at which a channel is formed is positive and as close to 0 V as possible without depending on the channel length, can be manufactured.

Provided is a semiconductor device which can suppress an increase in oxygen vacancies in an oxide semiconductor layer and a manufacturing method of the semiconductor device. The semiconductor device includes a first oxide semiconductor layer over the first insulating layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a third oxide semiconductor layer over the second oxide semiconductor layer; a source electrode layer and a drain electrode layer each over the third oxide semiconductor layer; a fourth semiconductor layer over the source and drain electrode layers, and the third oxide semiconductor layer; a gate insulating layer over the fourth oxide semiconductor layer; a gate electrode layer over the gate electrode layer and overlapping with the source and drain electrode layers, and the fourth oxide semiconductor layer; and a second insulating layer over the first insulating layer, and the source, gate, and drain electrode layers.

A High Electron Mobility Transistor (HEMT) and a process of forming the same are disclosed. The HEMT includes a substrate, a channel layer, a barrier layer, and heavily doped regions made of metal oxide. The channel layer and the barrier layer provide recesses and a mesa therebetween. The heavily doped regions are formed by partially removing in a portion thereof on the mesa and have slant surfaces facing the gate electrode. The slant surfaces make angle of 135° to 160° against the top horizontal level of the mesa.

This disclosure provides thin film transistors (TFTs) including p-n hetero-junction structures. A p-n hetero-junction structure may include a junction between a narrow bandgap material and a wide bandgap material. The narrow bandgap material, which may be an oxide, nitride, selenide, or sulfide, is the active channel material of the TFT and may provide relatively high carrier mobility. The hetero-junction structures facilitate band-to-band tunneling and suppression of TFT off-currents. In various implementations, the TFTs may be formed on flexible substrates and have low temperature processing capabilities.

After a sputtering gas is supplied to a deposition chamber, plasma including an ion of the sputtering gas is generated in the vicinity of a target. The ion of the sputtering gas is accelerated and collides with the target, so that flat-plate particles and atoms of the target are separated from the target. The flat-plate particles are deposited with a gap therebetween so that the flat plane faces a substrate. The atom and the aggregate of the atoms separated from the target enter the gap between the deposited flat-plate particles and grow in the plane direction of the substrate to fill the gap. A film is formed over the substrate. After the deposition, heat treatment is performed at high temperature in an oxygen atmosphere, which forms an oxide with a few oxygen vacancies and high crystallinity.

The present invention provides a TFT substrate manufacturing method and a TFT substrate manufactured with the method. The TFT substrate manufacturing method of the present invention uses a photoresist pattern to serve as a shielding mask to allow a metal layer to be directly oxidized, through the anodic oxidation technology, into a gate insulation layer or a passivation layer, and at the same time, forming electrode patterns of gate or source/drain. The entire operation can be conducted in room temperature and is applicable to a flexible substrate that is not resistant to high temperatures without the involvement of expensive high temperature facility, such as chemical vapor deposition, so as to greatly reduce the operation cost of manufacturing a flexible display device. The TFT substrate manufactured with the present invention shows excellent electrical characteristics and is suitable for a flexible display device.

A semiconductor device including a first oxide semiconductor layer, a first gate electrode opposing the first oxide semiconductor layer, a first gate insulating layer between the first oxide semiconductor layer and the first gate electrode, a first insulating layer covering the first oxide semiconductor layer and having a first opening, a first conductive layer above the first insulating layer and in the first opening, the first conductive layer being electrically connected to the first oxide semiconductor layer, and an oxide layer between an upper surface of the first insulating layer and the first conductive layer, wherein the first insulating layer is exposed from the oxide layer in a region not overlapping the first conductive layer in a plan view.

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.