A semiconductor memory device including a substrate; a semiconductor pattern extending in a first horizontal direction on the substrate; bit lines extending in a second horizontal direction on the substrate perpendicular to the first horizontal direction, the bit lines being at a first end of the semiconductor pattern; word lines extending in a vertical direction on the substrate at a side of the semiconductor pattern; a capacitor structure on a second end of the semiconductor pattern opposite to the first end in the first horizontal direction, the capacitor structure including a lower electrode connected to the semiconductor pattern, an upper electrode spaced apart from the lower electrode, and a capacitor dielectric layer between the lower electrode and the upper electrode; and a capacitor contact layer between the second end of the semiconductor pattern and the lower electrode and including a pair of convex surfaces in contact with the semiconductor pattern.

Disclosed is a semiconductor device having a memory cell which comprises a transistor having a control gate and a storage gate. The storage gate comprises an oxide semiconductor and is able to be a conductor and an insulator depending on the potential of the storage gate and the potential of the control gate. Data is written by setting the potential of the control gate to allow the storage gate to be a conductor, supplying a potential of data to be stored to the storage gate, and setting the potential of the control gate to allow the storage gate to be an insulator. Data is read by supplying a potential for reading to a read signal line connected to one of a source and a drain of the transistor and detecting the change in potential of a bit line connected to the other of the source and the drain.

A semiconductor device having favorable electric characteristics and a manufacturing method thereof are provided. A transistor includes an oxide semiconductor layer formed over an insulating layer, a source electrode layer and a drain electrode layer which overlap with part of the oxide semiconductor layer, a gate insulating layer in contact with part of the oxide semiconductor layer, and a gate electrode layer over the gate insulating layer. In the transistor, a buffer layer having n-type conductivity is formed between the source electrode layer and the oxide semiconductor layer and between the drain electrode layer and the oxide semiconductor layer. Thus, parasitic resistance is reduced, resulting in improvement of on-state characteristics of the transistor.

Provided are an oxide sintered compact whereby low carrier density and high carrier mobility are obtained when the oxide sintered compact is used to obtain an oxide semiconductor thin film by a sputtering method, and a sputtering target which uses the oxide sintered compact. This oxide sintered compact contains oxides of indium, gallium, and aluminum. The gallium content is from 0.15 to 0.49 by Ga/(In+Ga) atomic ratio, and the aluminum content is from 0.0001 to less than 0.25 by Al/(In+Ga+Al) atomic ratio. A crystalline oxide semiconductor thin film formed using this oxide sintered compact as a sputtering target is obtained at a carrier density of 4.0×10.sup.18 cm.sup.−3 or less and a carrier mobility of 10 cm.sup.−2V.sup.−1sec.sup.−1 or greater.

Provided is a semiconductor device of the embodiment including: an oxide semiconductor layer; a gate electrode; a first electrode electrically connected to one portion of the oxide semiconductor layer, the first electrode including a first region, second region, a third region, and a fourth region, the first region disposed between the first portion and the second region, the first region disposed between the third region and the fourth region, the first region containing at least one element of In, Zn, Sn or Cd, and oxygen, the second region containing at least one metal element of Ti, Ta, W, or Ru, the third region and the fourth region containing the at least one metal element and oxygen, the third region and the fourth region having an atomic concentration of oxygen higher than that of the second region; and a second electrode electrically connected to another portion of the oxide semiconductor layer.

A semiconductor device includes a power switch circuit and a logic circuit. The semiconductor device includes a first dielectric layer and a thin film transistor (TFT) formed on the first dielectric layer. The TFT includes a semiconductor nano-sheet, a gate dielectric layer wrapping around a channel region of the semiconductor nano-sheet, and a gate electrode layer formed on the gate dielectric layer. The semiconductor nano-sheet is made of an oxide semiconductor material.

A method of manufacturing a TFT substrate includes the steps of forming an oxide semiconductor layer above a substrate, forming a first oxide film on the oxide semiconductor layer, performing oxidation processing on the oxide semiconductor layer after formation of the first oxide film, and forming a second oxide film on the first oxide film after the oxidation processing.

A highly reliable semiconductor device including an oxide semiconductor is provided. Provided is a semiconductor device including an oxide semiconductor layer, an insulating layer in contact with the oxide semiconductor layer, a gate electrode layer overlapping with the oxide semiconductor layer, and a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor layer. The oxide semiconductor layer includes a first region having a crystal whose size is less than or equal to 10 nm and a second region which overlaps with the insulating layer with the first region provided therebetween and which includes a crystal part whose c-axis is aligned in a direction parallel to a normal vector of the surface of the oxide semiconductor layer.

An electronic device including a two-dimensional electron gas is provided. The electronic device includes a substrate, a first material layer disposed on the substrate and formed of a binary oxide, a second material layer disposed on the first material layer and formed of a binary oxide, and a two-dimensional electron gas generated between the first material layer and the second material layer.

Disclosed is a method for manufacturing a TFT substrate, which uses one partial transmitting mask to form patterns of an active layer, a gate insulation layer, and a gate electrode through photolithography such that the entire process for manufacturing TFT substrate can be completely conducted by using only three masks. Compared to the prior art, one mask is save so that the operation is simplified and the manufacturing cost is reduced.