Liquid crystal display device having polycrystalline silicon thin film transistor and method of fabricating the same

1. A method of fabricating an array substrate for a liquid crystal display (LCD) device, comprising:

forming at least an alignment key on a substrate, the substrate having a first region and a second region, wherein the alignment key is substantially located in the second region;

forming an amorphous silicon layer on the alignment key;

crystallizing a predetermined portion of the amorphous silicon layer using the alignment key as a reference;

patterning the amorphous silicon layer using the alignment key as a reference to form a polycrystalline silicon layer, wherein the polycrystalline silicon layer is formed from the predetermined portion of the amorphous silicon layer;

forming a gate insulating layer on the polycrystalline silicon layer;

forming a gate electrode on the gate insulating layer using the alignment key as a reference;

forming an interlayer insulating layer on the gate electrode; and

forming source and drain electrodes on the interlayer insulating layer.

2. The method according to claim 1 , wherein the crystallizing includes performing a sequential lateral solidification method.

3. The method according to claim 1 , further comprising forming a buffer layer between the alignment key and the amorphous silicon layer.

4. The method according to claim 3 , further comprising forming a color filter layer between the substrate and the buffer layer.

5. The method according to claim 4 , wherein the alignment key is formed from the same material as the color filter layer.

6. The method according to claim 4 , wherein the alignment key is formed from the same layer as the color filter layer.

7. The method according to claim 5 , wherein the alignment key is formed in the non-display region.

8. The method according to claim 5 , wherein the color filter layer is formed in the display region.

9. The method according to claim 4 , wherein the color filter layer includes red, green and blue color sub-filters.

10. The method according to claim 4 , wherein the color filter layer thermally insulates the substrate from the amorphous silicon layer.

11. The method according to claim 1 , further comprising doping the polycrystalline silicon layer with impurities using the gate electrode as a doping mask.

12. The method according to claim 11 , further comprising activating the semiconductor layer.

13. The method according to claim 12 , wherein the activating includes performing a laser annealing method.

14. A method of fabricating a liquid crystal display (LCD) device, comprising;

forming at least an alignment key on a first substrate, having a first region and a second region, wherein the alignment key is substantially located in the second region;

forming an amorphous silicon layer on the alignment key;

crystallizing a predetermined portion of the amorphous silicon layer using the alignment key as a reference;

patterning the amorphous silicon layer using the alingment key as a reference to form a polycrystalline silicon layer, when the polycrystalline silicon layer is formed from the predetermined portion of the amorphous silicon layer;

forming a gate insulating layer on the semiconductor layer;

forming a gate electrode on the gate insulating layer using the alignment key as reference;

forming an interlayer insulating layer on the gate electrode;

forming source and drain electrodes on the interlayer insulating layer;

forming a passivation layer on the source and drain electrodes;

forming a pixel electrode on the passivation layer;

forming a common electrode on a second substrate;

attaching the first and second substrates such that the pixel electrode faces the common electrode; and

forming a liquid crystal layer between the pixel elecrode and the common electrode.

15. The method according to claim 14 , further comprising;

forming a buffer later between the alignment key and the amorphous silicon layer; and

forming a color filter layer between the substrate and the buffer layer,

wherein the alignment key is formed of the same material as the color filter layer.

16. The method according to claim 15 , wherein the alignment key is formed of the same layer as the color filter layer.