A Thin Film Transistor (TFT) includes a substrate, a semiconductor layer disposed on the substrate a first source electrode and a first drain electrode spaced apart from each other on the semiconductor layer, a channel area disposed in the semiconductor layer between the first source electrode and the first drain electrode, an etching prevention layer disposed on the channel area, the first source electrode, and the first drain electrode and a second source electrode in contact with the first source electrode, and a second drain electrode in contact with the first drain electrode.

Embodiments of the present disclosure provide a thin film transistor (TFT) and a method of manufacturing the same, which enables to decrease the vertical resistance from the source and the drain to the polarity inversion region, so that the current from the source and the drain to the polarity inversion region may be increased, thereby improving the performances of the TFT. An active layer of the TFT is provided with a first groove and a second groove which neither pass through the active layer. A source and a drain of the TFT are formed at least partially in the first groove and the second groove, respectively. The source and the drain contact the active layer through the first groove and the second groove, respectively.

A metal oxide semiconductor transistor includes a gate, a metal oxide active layer, a gate insulating layer, a source, and a drain. The metal oxide active layer has a first surface and a second surface, and the first surface faces to the gate. The gate insulating layer is disposed between the gate and the metal oxide active layer. The source and the drain are respectively connected to the metal oxide active layer. The second surface defines a mobility enhancing region between the source and the drain. An oxygen content of the metal oxide active layer in the mobility enhancing region is less than an oxygen content of the metal oxide active layer in the region outside the mobility enhancing region. The metal oxide semiconductor transistor has high carrier mobility.

A display may have upper and lower display layers. A layer of liquid crystal material may be interposed between the upper and lower display layers. The display layers may have substrates. The display layers may include a color filter layer having an array of color filter elements on a glass substrate and a thin-film transistor layer having a layer of thin-film transistor circuitry on a glass substrate. Dielectric layers within the display layers such as dielectric layers within the thin-film transistor layer may have differing indices of refraction. Reflections and color shifts due to index of refraction discontinuities may be minimized by interposing graded index dielectric layers between adjacent layers with different indices. The graded index layers may be formed from structures with a continuously varying index of refraction or structures with a step-wise varying index of refraction.

In a semiconductor device including a transistor including an oxide semiconductor film and a protective film over the transistor, an oxide insulating film containing oxygen in excess of the stoichiometric composition is formed as the protective film under the following conditions: a substrate placed in a treatment chamber evacuated to a vacuum level is held at a temperature higher than or equal to 180 C. and lower than or equal to 260 C.; a source gas is introduced into the treatment chamber so that the pressure in the treatment chamber is set to be higher than or equal to 100 Pa and lower than or equal to 250 Pa; and a high-frequency power higher than or equal to 0.17 W/cm.sup.2 and lower than or equal to 0.5 W/cm.sup.2 is supplied to an electrode provided in the treatment chamber.

A semiconductor device and a manufacturing method thereof are provided. The semiconductor device includes an oxide semiconductor protrusion, a source, a drain, an oxide semiconductor layer, a first O-barrier layer, a gate electrode, a second O-barrier layer, and an H-barrier layer. The oxide semiconductor protrusion is disposed on an oxide substrate. The source and the drain are respectively disposed on opposite ends of the oxide semiconductor protrusion. The oxide semiconductor layer is disposed on the oxide substrate and covers the oxide semiconductor protrusion, the source, and the drain. The first O-barrier layer is disposed on the oxide semiconductor layer. The gate electrode is disposed on the first O-barrier layer and across the oxide semiconductor protrusion. The second O-barrier layer is disposed on the gate electrode. The H-barrier layer is disposed on the oxide substrate and covers the second O-barrier layer.

To achieve high processing capability, a semiconductor device includes first and second circuits, first to third wirings, and first to fourth transistors. The first circuit is electrically connected to the first wiring and a gate of the first transistor. One of a source and a drain of the first transistor is electrically connected to the second wiring. The other of the source and the drain of the first transistor is electrically connected to a gate of the second transistor. The second circuit is electrically connected to the first wiring and a gate of the third transistor. One of a source and a drain of the third transistor is electrically connected to the third wiring. The other of the source and the drain of the third transistor is electrically connected to a gate of the fourth transistor. One of a source and a drain of the fourth transistor is electrically connected to one of a source and a drain of the second transistor. The other of the source and the drain of the fourth transistor is electrically connected to the other of the source and the drain of the second transistor.

A semiconductor device with an improved arithmetic processing speed and a decreased circuit size, and its driving method are provided. In the semiconductor device, a first terminal of a first transistor and a gate of a second transistor are electrically connected to a first terminal of a capacitor, and a control circuit is electrically connected to a second terminal of the capacitor. The control circuit supplies a first potential to the second terminal of the capacitor, in other words, adds a value corresponding to the first potential to the value of first data previously retained in the gate of the second transistor in order to obtain second data. In the second transistor, the second data, specifically, a third potential commensurate with the potential of the gate will be output from a second terminal when a second potential is supplied to a first terminal.

It is an object to manufacture a highly reliable display device using a thin film transistor having favorable electric characteristics and high reliability as a switching element. In a bottom gate thin film transistor including an amorphous oxide semiconductor, an oxide conductive layer having a crystal region is formed between an oxide semiconductor layer which has been dehydrated or dehydrogenated by heat treatment and each of a source electrode layer and a drain electrode layer which are formed using a metal material. Accordingly, contact resistance between the oxide semiconductor layer and each of the source electrode layer and the drain electrode layer can be reduced; thus, a thin film transistor having favorable electric characteristics and a highly reliable display device using the thin film transistor can be provided.

In a semiconductor device including a transistor, the transistor is provided over a first insulating film, and the transistor includes an oxide semiconductor film over the first insulating film, a gate insulating film over the oxide semiconductor film, a gate electrode over the gate insulating film, a second insulating film over the oxide semiconductor film and the gate electrode, and a source and a drain electrodes electrically connected to the oxide semiconductor film. The first insulating film includes oxygen. The second insulating film includes hydrogen. The oxide semiconductor film includes a first region in contact with the gate insulating film and a second region in contact with the second insulating film. The first insulating film includes a third region overlapping with the first region and a fourth region overlapping with the second region. The impurity element concentration of the fourth region is higher than that of the third region.