Organic light emitting diode display having dual gate thin film transistors

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

a substrate;

a scan line formed on the substrate and configured to transmit a scan signal;

a data line and a driving voltage line crossing the scan line and respectively configured to transmit a data signal and a driving voltage;

a switching thin film transistor operatively connected to the scan line and the data line;

a driving thin film transistor operatively connected to the switching thin film transistor and the driving voltage line;

a compensation thin film transistor configured to compensate a threshold voltage of the driving thin film transistor and operatively connected to the driving thin film transistor; and

an OLED operatively connected to the driving thin film transistor,

wherein the compensation thin film transistor comprises a first compensation gate electrode and a second compensation gate electrode separated from each other and formed over different layers, and wherein the first and second compensation gate electrodes do not overlap each other in the depth dimension of the OLED display,

wherein the compensation thin film transistor further comprises:

a compensation semiconductor layer formed on the substrate;

a first gate insulating layer covering the compensation semiconductor layer, wherein the first compensation gate electrode is formed over the first gate insulating layer; and

a second gate insulating layer covering the first gate insulating layer and the first compensation gate electrode, wherein the second compensation gate electrode is formed over the second gate insulating layer, and

wherein the compensation semiconductor layer, the first gate insulating layer, the first compensation gate electrode, the second gate insulating layer, and the second compensation gate electrode are sequentially disposed on the substrate in perpendicular direction to the substrate.

2. The OLED display of claim 1 , wherein the compensation thin film transistor further comprises a compensation source electrode and a compensation drain electrode, wherein the first compensation gate electrode is adjacent to the compensation source electrode, and

wherein the second compensation gate electrode is adjacent to the compensation drain electrode.

3. The OLED display of claim 1 , wherein the first compensation gate electrode is electrically connected to the second compensation gate electrode through a gate contact hole formed in the second gate insulating layer.

4. The OLED display of claim 2 , wherein the first and second compensation gate electrodes are substantially parallel to each other.

5. The OLED display of claim 2 , wherein the first and second compensation gate electrodes are formed with an angle therebetween.

6. The OLED display of claim 3 , wherein the first compensation gate electrode and the scan line are formed on the same layer.

7. The OLED display of claim 1 , further comprising:

an initialization thin film transistor configured to be turned on according to a previous scan signal transmitted through a previous scan line and configured to transmit an initialization voltage to the driving gate electrode of the driving thin film transistor, and

wherein the initialization thin film transistor comprises a first initialization gate electrode and a second initialization gate electrode that are separated from each other and formed over different layers.

8. The OLED display of claim 7 , wherein the initialization thin film transistor further comprises:

an initialization semiconductor layer formed on the substrate, and

wherein the first initialization gate electrode is formed on a first gate insulating layer covering the initialization semiconductor layer,

and the second initialization gate electrode is formed on a second gate insulating layer covering the first gate insulating layer and the first initialization gate electrode.

9. The OLED display of claim 8 , wherein the initialization thin film transistor further comprises an initialization source electrode and an initialization drain electrode, wherein the first initialization gate electrode is adjacent to the initialization source electrode, and

wherein the second initialization gate electrode is adjacent to the initialization drain electrode.

10. The OLED display of claim 8 , wherein the first initialization gate electrode is electrically connected to the second initialization gate electrode through a gate contact hole formed in the second gate insulating layer.

11. The OLED display of claim 8 , wherein the first and second initialization gate electrodes are substantially parallel to each other.

12. The OLED display of claim 8 , wherein the first and second initialization gate electrodes are formed with an angle therebetween.

13. The OLED display of claim 7 , wherein the first initialization gate electrode and the scan line are formed on the same layer.

14. The OLED display of claim 7 , wherein the switching thin film transistor includes a first switching gate electrode and a second switching gate electrode separated from each other and formed over different layers.

15. The OLED display of claim 14 , wherein the switching thin film transistor further comprises:

a switching semiconductor layer formed on the substrate;

a first gate insulating layer covering the switching semiconductor layer, wherein the first switching gate electrode is formed over the first gate insulating layer; and

a second gate insulating layer covering the first gate insulating layer and the first switching gate electrode, wherein the second switching gate electrode is formed over the second gate insulating layer.

16. The OLED display of claim 15 , wherein the switching thin film transistor further comprises a switching source electrode and a switching drain electrode, wherein the first switching gate electrode is adjacent to the switching source electrode, and

wherein the second switching gate electrode is adjacent to the switching drain electrode.

17. The OLED display of claim 15 , wherein the first switching gate electrode is electrically connected to the second switching gate electrode through a gate contact hole formed in the second gate insulating layer.

18. The OLED display of claim 7 , further comprising:

a light emission control thin film transistor configured to be turned on by a light emission control signal transmitted through the light emission control line and configured to transmit the driving voltage from the driving thin film transistor to the OLED, and

wherein the light emission control thin film transistor comprises a first light emission control gate electrode and a second light emission control gate electrode that are separated from each other and formed over different layers.

19. The OLED display of claim 18 , wherein the light emission control thin film transistor further comprises:

a light emission control semiconductor layer formed on the substrate, and

wherein the first light emission control gate electrode is formed on a first gate insulating layer covering the light emission control semiconductor layer,

and the second light emission control gate electrode is formed on a second gate insulating layer covering the first gate insulating layer and the first light emission control gate electrode.

20. The OLED display of claim 19 , wherein the light emission control thin film transistor further comprises a light emission control source electrode and a light emission control drain electrode, wherein the first light emission control gate electrode is adjacent to the light emission control source electrode, and

wherein the second light emission control gate electrode is adjacent to the light emission control drain electrode.

21. The OLED display of claim 19 , wherein the first light emission control gate electrode is electrically connected to the second light emission control gate electrode through a gate contact hole formed in the second gate insulating layer.

22. The OLED display of claim 18 , further comprising:

an operation control thin film transistor configured to be turned on by a light emission control signal transmitted through the light emission control line and configured to transmit the driving voltage to the driving thin film transistor, and

wherein the operation control thin film transistor comprises a first operation control gate electrode and a second operation control gate electrode that are separated from each other and formed over different layers.

23. The OLED display of claim 22 , wherein the operation control thin film transistor further comprises:

an operation control semiconductor layer formed on the substrate, and

wherein the first operation control gate electrode is formed on a first gate insulating layer covering the operation control semiconductor layer,

and the second operation control gate electrode is formed on a second gate insulating layer covering the first gate insulating layer and the first operation control gate electrode.

24. The OLED display of claim 23 , wherein the operation control thin film transistor further comprises an operation control source electrode and an operation control drain electrode, wherein the first operation control gate electrode is adjacent to the operation control source electrode, and

wherein the second operation control gate electrode is adjacent to the operation control drain electrode.

25. The OLED display of claim 23 , wherein the first operation control gate electrode is electrically connected to the second operation control gate electrode through a gate contact hole formed in the second gate insulating layer.

26. The OLED display of claim 1 , wherein the second compensation gate electrode is farther from the substrate than the first compensation gate electrode, and wherein the second compensation gate electrode is wider than the first compensation gate electrode.