Display substrate, method of manufacturing the same, and display device including the same
A display substrate includes a substrate, a first gate electrode on the substrate, a first gate insulating layer on the first gate electrode, an active layer on the first gate insulating layer, a second gate insulating layer on the active layer, a second gate electrode on the second gate insulating layer, an interlayer insulating layer on the second gate electrode, a first electrode on the interlayer insulating layer to contact a top surface, a side wall, and a bottom surface of the active layer via a first contact hole through the interlayer insulating layer, the second gate insulating layer, the active layer, and a portion of the first gate insulating layer, and a second electrode on the interlayer insulating layer to contact the first gate electrode via a second contact hole through the interlayer insulating layer, the second gate insulating layer, and the first gate insulating layer.
1. A display substrate comprising:
a substrate;
a first gate electrode on the substrate;
a first gate insulating layer on the substrate to cover the first gate electrode;
an active layer on the first gate insulating layer;
a second gate insulating layer on the first gate insulating layer to cover the active layer;
a second gate electrode on the second gate insulating layer;
an interlayer insulating layer on the second gate insulating layer to cover the second gate electrode;
a first electrode on the interlayer insulating layer to directly contact a top surface, a side wall, and a bottom surface of the active layer via a first contact hole through the interlayer insulating layer, the second gate insulating layer, the active layer, and a portion of the first gate insulating layer; and
a second electrode on the interlayer insulating layer to directly contact the first gate electrode via a second contact hole through the interlayer insulating layer, the second gate insulating layer, and the first gate insulating layer,
wherein the first gate insulating layer comprises:
a first sub-insulating layer on the substrate to cover the first gate electrode; and
a second sub-insulating layer on the first sub-insulating layer, the second sub-insulating layer being different in material from the first sub-insulating layer, and
wherein the second contact hole extends through the first sub-insulating layer and the second sub-insulating layer.
2. The display substrate of claim 1 , wherein the second electrode directly contacts a top surface of the first gate electrode via the second contact hole.
3. The display substrate of claim 1 , wherein the first contact hole comprises:
a first portion formed through the second gate insulating layer to expose the top surface of the active layer;
a second portion formed through the active layer to expose the side wall of the active layer; and
a third portion formed through the portion of the first gate insulating layer to expose the bottom surface of the active layer.
4. The display substrate of claim 3 , wherein a width of the first portion is greater than a width of the second portion.
5. The display substrate of claim 3 , wherein a width of the third portion is greater than a width of the second portion.
6. The display substrate of claim 1 , wherein the portion of the first gate insulating layer is a portion of the second sub-insulating layer.
7. The display substrate of claim 1 , wherein the first sub-insulating layer comprises silicon nitride.
8. The display substrate of claim 1 , wherein the second sub-insulating layer comprises silicon oxide.
9. The display substrate of claim 1 , wherein the active layer comprises polycrystalline silicon.
10. The display substrate of claim 1 , wherein the second gate insulating layer comprises silicon oxide.
11. The display substrate of claim 1 , wherein the first gate electrode overlaps the second gate electrode with the active layer interposed therebetween.
12. The display substrate of claim 1 , wherein the interlayer insulating layer comprises:
a first interlayer insulating layer on the second gate insulating layer to cover the second gate electrode; and
a second interlayer insulating layer on the first interlayer insulating layer.
13. The display substrate of claim 12 , wherein the first interlayer insulating layer comprises silicon nitride.
14. The display substrate of claim 12 , further comprising a capacitor electrode between the first interlayer insulating layer and the second interlayer insulating layer, and overlapping the second gate electrode.
15. The display substrate of claim 1 , wherein a top surface of the first electrode and a top surface of the second electrode are coplanar.
16. A display device comprising:
a substrate;
a first gate electrode on the substrate;
a first gate insulating layer on the substrate to cover the first gate electrode;
an active layer on the first gate insulating layer;
a second gate insulating layer on the first gate insulating layer to cover the active layer;
a second gate electrode on the second gate insulating layer;
an interlayer insulating layer on the second gate insulating layer to cover the second gate electrode;
a first electrode on the interlayer insulating layer to directly contact a top surface, a side wall, and a bottom surface of the active layer via a first contact hole through the interlayer insulating layer, the second gate insulating layer, the active layer, and a portion of the first gate insulating layer;
a second electrode on the interlayer insulating layer to directly contact the first gate electrode via a second contact hole through the interlayer insulating layer, the second gate insulating layer, and the first gate insulating layer;
a planarization layer on the interlayer insulating layer to cover the first electrode and the second electrode;
a pixel electrode on the planarization layer;
a counter electrode overlapping the pixel electrode; and
a light emitting layer between the pixel electrode and the counter electrode,
wherein the first gate insulating layer comprises:
a first sub-insulating layer on the substrate to cover the first gate electrode; and
a second sub-insulating layer on the first sub-insulating layer, the second sub-insulating layer being different in material from the first sub-insulating layer, and
wherein the second contact hole extends through the first sub-insulating layer and the second sub-insulating layer.