According to one embodiment, a method of manufacturing a semiconductor device, includes forming a first insulating layer, an oxide semiconductor layer, a second insulating layer, a buffer layer and a metal layer sequentially on a base, forming a patterned resist on the metal layer, etching the buffer layer and the metal layer using the resist as a mask to expose an upper surface of the second insulating layer, reducing a volume of the resist to expose an upper surface along a side surface of the metal layer, etching the metal layer using the resist as a mask, to form a gate electrode and to expose an upper surface of the buffer layer, and carrying out ion implantation on the oxide semiconductor layer using the gate electrode as a mask.

Disclosed are a thin film transistor, a method of manufacturing the same, and an array substrate. The thin film transistor includes a substrate, a gate, a gate insulating layer, an active layer, an ohmic contact layer, and a source-drain electrode layer, the gate insulating layer includes at least a first gate insulating layer deposited at a low rate, a second gate insulating layer deposited at a high rate, and a third gate insulating layer deposited at a low rate, the first gate insulating layer is in contact with the gate, the third gate insulating layer is in contact with the active layer, and the first gate insulating layer and the third gate insulating layer have a density greater than a density of the second gate insulating layer.

As a display device has a higher definition, the number of pixels, gate lines, and signal lines are increased. When the number of the gate lines and the signal lines are increased, a problem of higher manufacturing cost, because it is difficult to mount an IC chip including a driver circuit for driving of the gate and signal lines by bonding or the like. A pixel portion and a driver circuit for driving the pixel portion are provided over the same substrate, and at least part of the driver circuit includes a thin film transistor using an oxide semiconductor interposed between gate electrodes provided above and below the oxide semiconductor. Therefore, when the pixel portion and the driver portion are provided over the same substrate, manufacturing cost can be reduced.

A transistor with stable electrical characteristics. A semiconductor device includes a first insulator over a substrate, a second insulator over the first insulator, an oxide semiconductor in contact with at least part of a top surface of the second insulator, a third insulator in contact with at least part of a top surface of the oxide semiconductor, a first conductor and a second conductor electrically connected to the oxide semiconductor, a fourth insulator over the third insulator, a third conductor which is over the fourth insulator and at least part of which is between the first conductor and the second conductor, and a fifth insulator over the third conductor. The first insulator contains a halogen element.

Disclosed herein are dual gate trench shaped thin film transistors and related methods and devices. Exemplary thin film transistor structures include a non-planar semiconductor material layer having a first portion extending laterally over a first gate dielectric layer, which is over a first gate electrode structure, and a second portion extending along a trench over the first gate dielectric layer, a second gate electrode structure at least partially within the trench, and a second gate dielectric layer between the second gate electrode structure and the first portion.

A transistor with small parasitic capacitance can be provided. A transistor with high frequency characteristics can be provided. A semiconductor device including the transistor can be provided. Provided is a transistor including an oxide semiconductor, a first conductor, a second conductor, a third conductor, a first insulator, and a second insulator. The first conductor has a first region where the first conductor overlaps with the oxide semiconductor with the first insulator positioned therebetween; a second region where the first conductor overlaps with the second conductor with the first and second insulators positioned therebetween; and a third region where the first conductor overlaps with the third conductor with the first and second insulators positioned therebetween. The oxide semiconductor including a fourth region where the oxide semiconductor is in contact with the second conductor; and a fifth region where the oxide semiconductor is in contact with the third conductor.

A semiconductor device comprises a first insulating layer, an oxide semiconductor layer having a polycrystalline structure on the first insulating layer, a gate insulating layer on the oxide semiconductor layer, a gate wiring on the gate insulating layer, and a second insulating layer on the gate wiring. The oxide semiconductor layer has a first region, a second region and a third region aligned toward a first direction. The first region overlaps the gate insulating layer and the gate wiring. The third region is in contact with the second insulating layer. A distance from a top surface of the second region to a top surface of the second insulating layer is longer than a distance from a top surface of the third region to the top surface of the second insulating layer.

A semiconductor device according to an embodiment includes an oxide semiconductor layer provided above an insulating surface, a gate insulating layer provided above the oxide semiconductor layer, and a gate electrode provided above the oxide semiconductor layer via the gate insulating layer, wherein the gate electrode has a titanium-containing layer and a conductive layer in order from the gate insulating layer side, the gate insulating layer includes a first region overlapping the gate electrode and a second region not overlapping the gate electrode, and a thickness of the titanium-containing layer is 50% or less than a thickness of the gate insulating layer in the first region.

The invention allows stable fabrication of a TFT circuit board used in a display device and having thereon an oxide semiconductor TFT. A TFT circuit board includes a TFT that includes an oxide semiconductor. The TFT has a gate insulating film formed on part of the oxide semiconductor and a gate electrode formed on the gate insulating film. A portion of the oxide semiconductor that is covered with the gate electrode 104 and a portion of the oxide semiconductor that is not covered with the gate electrode are both covered with a first interlayer insulating film. The first interlayer insulating film is covered with a first film 106, and the first film is covered with a first AlO film.

A semiconductor device includes thin film transistors each having an oxide semiconductor. The oxide semiconductor has a channel region, a drain region, a source region, and low concentration regions which are lower in impurity concentration than the drain region and the source region. The low concentration regions are located between the channel region and the drain region, and between the channel region and the source region. Each of the thin film transistors has a gate insulating film on the channel region and the low concentration regions, an aluminum oxide film on a first part of the gate insulating film, the first part being located on the channel region, and a gate electrode on the aluminum oxide film and a second part of the gate insulating film, the second part being located on the low concentration regions.