Devices and methods for forming a device are disclosed. The method includes providing a crystalline-on-insulator substrate having a bulk substrate and a surface substrate separated by a buried insulator layer. The surface substrate is defined with a device region. A transistor having a gate is formed in the device region. A first diffusion region is formed adjacent to a first side of the gate and a second diffusion region is formed adjacent to and displaced away from a second side of the gate. At least a first drift isolation region is formed in the surface substrate adjacent to and underlaps the second side of the gate. A drift well is formed in the surface substrate encompassing the first drift isolation region. A device isolation region surrounding the device region is formed in the surface substrate. The device isolation region includes a second depth which is deeper than a first depth of the first drift isolation region.

Occurrence of short-channel characteristics and parasitic capacitance of a MOSFET on a SOI substrate is prevented. A sidewall having a stacked structure obtained by sequentially stacking a silicon oxide film and a nitride film is formed on a side wall of a gate electrode on the SOI substrate. Subsequently, after an epitaxial layer is formed beside the gate electrode, and then, the nitride film is removed. Then, an impurity is implanted into an upper surface of the semiconductor substrate with using the gate electrode and the epitaxial layer as a mask, so that a halo region is formed in only a region of the upper surface of the semiconductor substrate which is right below a vicinity of both ends of the gate electrode.

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.

An object is to provide a structure of a transistor which has a channel formation region formed using an oxide semiconductor and a positive threshold voltage value, which enables a so-called normally-on switching element. The transistor includes an oxide semiconductor stack in which at least a first oxide semiconductor layer and a second oxide semiconductor layer with different energy gaps are stacked and a region containing oxygen in excess of its stoichiometric composition ratio is provided.

An array substrate includes a substrate, driving TFTs, and switch TFTs directly on the substrate. The driving TFT includes a buffer layer, a gate, a first gate insulator layer, a second gate insulator layer, and a metal oxide semiconductor layer stacked in that order on the substrate, and a source electrode and a drain electrode coupled to the metal oxide semiconductor layer. The switch TFT includes a buffer layer, a gate, a second gate insulator layer, and a metal oxide semiconductor layer stacked in that order on the substrate, and a source electrode and a drain electrode coupled to the metal oxide semiconductor layer.

There are provided a method of manufacturing a thin film transistor and a display including a thin film transistor. The method of manufacturing a thin film transistor includes forming a barrier layer cm a substrate, forming a semiconductor layer on the barrier layer, forming a gate insulating layer on the semiconductor layer, forming a gate electrode on the gate insulating layer, forming an offset region on an external surface of the gate electrode through a plasma heat treatment process or an annealing process, etching, an offset region of the gate electrode, etching a gate insulating layer except for a portion of the gate insulating layer, positioned below the gate electrode, forming an interlayer insulating layer on the gate electrode, and etching, the interlayer insulating layer to form a source electrode and a drain electrode.

A thin-film transistor substrate and a display device comprising the same are provided which can improve display quality by reducing or preventing deterioration of the characteristics of thin-film transistors. The thin-film transistor substrate comprises thin-film transistors on a lower protective metal layer. Each thin-film transistor comprises a buffer layer, a semiconductor layer, a first insulating film, a gate electrode, a second insulating film, a source electrode and a drain electrode, and a first electrode. The lower protective metal layer is electrically connected to the gate electrode and overlaps the channel region of the semiconductor layer.

The present invention provides an amorphous silicon semiconductor TFT backboard structure, which includes a semiconductor layer (4) that has a multi-layer structure including a bottom amorphous silicon layer (41) in contact with a gate insulation layer (3), an N-type heavily-doped amorphous silicon layer (42) in contact with a source electrode (6) and a drain electrode (7), at least two N-type lightly-doped amorphous silicon layers (43) sandwiched between the bottom amorphous silicon layer (41) and the N-type heavily-doped amorphous silicon layer (42), a first intermediate amorphous silicon layer (44) separating every two adjacent ones of the lightly-doped amorphous silicon layers (43), and a second intermediate amorphous silicon layer (45) separating the N-type heavily-doped amorphous silicon layer (42) from the one of the lightly-doped amorphous silicon layers (43) that is closest to the N-type heavily-doped amorphous silicon layer (42). Such a structure further reduces the energy barrier between the drain electrode and the semiconductor layer, making injection of electron easier and ensuring the ON-state current is not lowered down and also helping increase the barrier for transmission of holes, lowering down the leakage current and improving reliability and electrical stability of the TFT.

One embodiment of the present invention is a semiconductor device at least including an oxide semiconductor film, a gate insulating film in contact with the oxide semiconductor film, and a gate electrode overlapping with the oxide semiconductor film with the gate insulating film therebetween. The oxide semiconductor film has a spin density lower than 9.310.sup.16 spins/cm.sup.3 and a carrier density lower than 110.sup.15/cm.sup.3. The spin density is calculated from a peak of a signal detected at a g value (g) of around 1.93 by electron spin resonance spectroscopy. The oxide semiconductor film is formed by a sputtering method while bias power is supplied to the substrate side and self-bias voltage is controlled, and then subjected to heat treatment.

An array substrate includes a substrate and data lines and scan lines arranged on the substrate. The data lines and the scan lines define plural pixel regions. A thin film transistor is arranged in each pixel region and includes a gate electrode, a source electrode, a drain electrode, and an active region. The gate electrode is arranged above the active region. The source electrode and the drain electrode are arranged at two opposite sides of the active region respectively. A light shielding metal layer is further arranged in each pixel region. The light shielding metal layer and the data lines are arranged in the same layer on the substrate. The light shielding metal layer is arranged under the active region and at least partially overlaps with the active region. The data line is close to the source electrode and does not overlap with the active region at least partially.