Display device
According to one embodiment, a display device includes a TFT on an insulating substrate. The TFT includes a gate electrode, an insulating layer on the gate electrode, a semiconductor layer on the insulating layer, and a source electrode and a drain electrode each provided in contact with at least a part of the semiconductor layer. The source and drain electrodes have a laminated structure including a lower layer, an intermediate layer and an upper layer. The source and drain electrodes include sidewalls each including a first tapered portion on the upper layer side, a second tapered portion on the lower layer side and a sidewall protective film attached to the second tapered portion. The taper angle of the first tapered portion is smaller than that of the second tapered portion.
1. A display device comprising:
a thin-film transistor comprising:
a gate electrode;
an insulating layer provided over the gate electrode;
a semiconductor layer over the insulating layer, at least a part of which is overlaid on the gate electrode, the semiconductor layer comprising a lower surface facing the insulating layer and an upper surface opposed to the lower surface; and
a source electrode and a drain electrode provided in contact with at least a part of the upper surface of the semiconductor layer, wherein
each of the source electrode and the drain electrode comprises a laminated structure including a lower layer located in the semiconductor layer side, an intermediate layer of aluminum as a main constituent and an upper layer, and
the source electrode and the drain electrode comprise sidewalls each comprising a first tapered portion on an upper layer side, a second tapered portion on a lower layer side, a taper angle of the first tapered portion being smaller than a taper angle of the second tapered portion, and a sidewall protective film provided on the second tapered portion in contact with the intermediate layer and formed of a CH-based material, or AlFx, and at least a part of the lower layer is positioned directly between the second tapered portion and the semiconductor layer and includes a side surface not covered by the sidewall protective film.
2. The display device of claim 1 , wherein a transition portion between the first tapered portion and the second tapered portion is located in the intermediate layer.
3. The display device of claim 2 , wherein the taper angle of the first tapered portion is 40° or less.
4. The display device of claim 2 , wherein the taper angle of the second tapered portion is 40° or more and 70° or less.
5. The display device of claim 1 , further comprising a protective layer configured to cover the source electrode, the drain electrode and the semiconductor layer,
wherein each of the source electrode and the drain electrode has a thickness of one third or more that of the protective layer.
6. The display device of claim 1 , wherein the upper layer and the lower layer are formed of a Ti- or Mo-based metal.
7. The display device of claim 1 , wherein the semiconductor layer is an oxide semiconductor layer of an oxide including at least one of indium (In), gallium (Ga) and zinc (Zn).
8. The display device of claim 1 , wherein the taper angle of the first tapered portion is 40° or less.
9. The display device of claim 1 , wherein the taper angle of the second tapered portion is 40° or more and 70° or less.
10. The display device of claim 1 , further comprising a protective layer configured to cover the source electrode, the drain electrode and the semiconductor layer,
wherein each of the source electrode and the drain electrode has a thickness of one third or more that of the protective layer.
11. The display device of claim 2 , wherein the upper layer and the lower layer are formed of a Ti- or Mo-based metal.
12. The display device of claim 2 , wherein the semiconductor layer is an oxide semiconductor layer of an oxide including at least one of indium (In), gallium (Ga) and zinc (Zn).