Organic light-emitting display device comprising multiple types of thin-film transistors and method of fabricating the same

1. An organic light-emitting display (OLED) device comprising:

a low-temperature poly-silicon (LTPS) thin-film transistor having a first channel layer, a first gate electrode, a first source electrode and a first drain electrode;

an oxide semiconductor thin-film transistor having a second channel layer, a second gate electrode, a second source electrode and a second drain electrode; and

a functional layer between the first channel layer and the first gate electrode,

wherein the second channel layer is in contact with an upper surface of the functional layer.

2. The OLED device of claim 1 , wherein the first gate electrode is on the functional layer,

the second gate electrode is on the second channel layer, and

the first gate electrode and the second gate electrode are made of the same material.

3. The OLED device of claim 2 , further comprising:

a first gate insulating layer between the second gate electrode and the second channel layer; and

a second gate insulating layer between the functional layer and the first gate electrode,

wherein the first gate insulating layer and the second gate insulating layer are made of the same material.

4. The OLED device of claim 3 , wherein the functional layer, together with the second gate insulating layer, functions as a gate insulating layer of the LTPS thin-film transistor, and

wherein a thickness of the functional layer is determined based on a thickness of the second gate insulating layer.

5. The OLED device of claim 1 , further comprising:

an interlayer insulating layer on the functional layer,

wherein the interlayer insulating layer covers both the first gate electrode and the second gate electrode.

6. The OLED device of claim 5 , wherein the interlayer insulating layer has a double insulation function, which insulates the first gate electrode of the LTPS thin-film transistor from the first source electrode and the first drain electrode and insulates the second gate electrode of the oxide semiconductor thin-film transistor from the second source electrode and the second drain electrode at the same time.

7. The OLED device of claim 5 , wherein the interlayer insulating layer includes:

a first interlayer insulating layer on the first gate electrode and the second gate electrode, and

a second interlayer insulating layer on the first interlayer insulating layer.

8. The OLED device of claim 7 , wherein a hydrogen content of the first interlayer insulating layer is lower than a hydrogen content of the second interlayer insulating layer.

9. The OLED device of claim 5 , wherein the first source electrode, the first drain electrode, the second source electrode and the second drain electrode are on the interlayer insulating layer, and

wherein the first source electrode, the first drain electrode, the second source electrode and the second drain electrode are made of a same material and have a same thickness.