A novel semiconductor device including an oxide semiconductor is provided. In particular, a planar semiconductor device including an oxide semiconductor is provided. A semiconductor device including an oxide semiconductor and having large on-state current is provided. The semiconductor device includes an oxide insulating film, an oxide semiconductor film over the oxide insulating film, a source electrode and a drain electrode in contact with the oxide semiconductor film, a gate insulating film between the source electrode and the drain electrode, and a gate electrode overlapping the oxide semiconductor film with the gate insulating film. The oxide semiconductor film includes a first region overlapped with the gate electrode and a second region not overlapped with the gate electrode, the source electrode, and the drain electrode. The first region and the second region have different impurity element concentrations. The gate electrode, the source electrode, and the drain electrode contain the same metal element.

A novel semiconductor device including an oxide semiconductor is provided. In particular, a planar semiconductor device including an oxide semiconductor is provided. A semiconductor device including an oxide semiconductor and having large on-state current is provided. The semiconductor device includes an oxide insulating film, an oxide semiconductor film over the oxide insulating film, a source electrode and a drain electrode in contact with the oxide semiconductor film, a gate insulating film between the source electrode and the drain electrode, and a gate electrode overlapping the oxide semiconductor film with the gate insulating film. The oxide semiconductor film includes a first region overlapped with the gate electrode and a second region not overlapped with the gate electrode, the source electrode, and the drain electrode. The first region and the second region have different impurity element concentrations. The gate electrode, the source electrode, and the drain electrode contain the same metal element.

A method for manufacturing an array substrate, including steps of forming a semiconductor pattern, a gate electrode and a first insulation pattern sequentially on a base substrate at different layers, an orthogonal projection of the semiconductor pattern onto the base substrate covering an orthogonal projection of the first insulation pattern onto the base substrate, and the orthogonal projection of the first insulation pattern onto the base substrate covering an orthogonal projection of the gate electrode onto the base substrate, and subjecting the semiconductor pattern to ion implantation through a single ion implantation process using the first insulation pattern and the gate electrode as a mask plate, so as to form an active layer, a heavily-doped source electrode region, a lightly-doped source electrode region, a heavily-doped drain electrode region, and a lightly-doped drain electrode region.

Solved is a problem of attenuation of output amplitude due to a threshold value of a TFT when manufacturing a circuit with TFTs of a single polarity. In a capacitor (105), a charge equivalent to a threshold value of a TFT (104) is stored. When a signal is inputted thereto, the threshold value stored in the capacitor (105) is added to a potential of the input signal. The thus obtained potential is applied to a gate electrode of a TFT (101). Therefore, it is possible to obtain the output having a normal amplitude from an output terminal (Out) without causing the amplitude attenuation in the TFT (101).

A novel semiconductor device including an oxide semiconductor is provided. In particular, a planar semiconductor device including an oxide semiconductor is provided. A semiconductor device including an oxide semiconductor and having large on-state current is provided. The semiconductor device includes an oxide insulating film, an oxide semiconductor film over the oxide insulating film, a source electrode and a drain electrode in contact with the oxide semiconductor film, a gate insulating film between the source electrode and the drain electrode, and a gate electrode overlapping the oxide semiconductor film with the gate insulating film. The oxide semiconductor film includes a first region overlapped with the gate electrode and a second region not overlapped with the gate electrode, the source electrode, and the drain electrode. The first region and the second region have different impurity element concentrations. The gate electrode, the source electrode, and the drain electrode contain the same metal element.

Disclosed is an electroluminescence device having a substrate, a thin film transistor over the substrate, an insulating film over the thin film transistor, an electroluminescence element over the insulating film, a passivation film over the electroluminescence element, and a counter substrate over the passivation film. The electroluminescence element is configured to emit light through the counter substrate, and a space between the substrate and the counter substrate is filled with a filler. The electroluminescence device is featured by the tapered side surface of a gate electrode of the thin film transistor.

There is provided a thin film transistor having improved reliability. A gate electrode includes a first gate electrode having a taper portion and a second gate electrode with a width narrower than the first gate electrode. A semiconductor layer is doped with phosphorus of a low concentration through the first gate electrode. In the semiconductor layer, two kinds of n.sup.-type impurity regions are formed between a channel formation region and n.sup.+-type impurity regions. Some of the n.sup.-type impurity regions overlap with a gate electrode, and the other n.sup.-type impurity regions do not overlap with the gate electrode. Since the two kinds of n.sup.-type impurity regions are formed, an off current can be reduced, and deterioration of characteristics can be suppressed.

A high reliability semiconductor display device is provided. A semiconductor layer in the semiconductor display device has a channel forming region, an LDD region, a source region, and a drain region, and the LDD region overlaps a first gate electrode, sandwiching a gate insulating film.

Solved is a problem of attenuation of output amplitude due to a threshold value of a TFT when manufacturing a circuit with TFTs of a single polarity. In a capacitor (105), a charge equivalent to a threshold value of a TFT (104) is stored. When a signal is inputted thereto, the threshold value stored in the capacitor (105) is added to a potential of the input signal. The thus obtained potential is applied to a gate electrode of a TFT (101). Therefore, it is possible to obtain the output having a normal amplitude from an output terminal (Out) without causing the amplitude attenuation in the TFT (101).

This invention provides a semiconductor device having high operation performance and high reliability. An LDD region 707 overlapping with a gate wiring is arranged in an n-channel TFT 802 forming a driving circuit, and a TFT structure highly resistant to hot carrier injection is achieved. LDD regions 717, 718, 719 and 720 not overlapping with a gate wiring are arranged in an n-channel TFT 804 forming a pixel unit. As a result, a TFT structure having a small OFF current value is achieved. In this instance, an element belonging to the Group 15 of the Periodic Table exists in a higher concentration in the LDD region 707 than in the LDD regions 717, 718, 719 and 720.