Method of fabricating thin film transistor

1. A method of fabricating a CMOS thin film transistor, comprising:

providing a substrate having first and second regions;

forming an amorphous silicon layer on the substrate;

forming a capping layer on the entire top surface of the amorphous silicon layer;

depositing a metal catalyst on the capping layer;

performing a first annealing process on the substrate to diffuse the metal catalyst through the capping layer to an interface of the amorphous silicon and the capping layer, and to crystallize the amorphous silicon layer into a polysilicon layer using the diffused metal catalyst;

removing the capping layer;

patterning the polysilicon layer to form first and second semiconductor layers in the first and second regions, respectively;

forming a gate insulating layer and a gate electrode on the first and second semiconductor layers;

implanting first impurities into the first and second semiconductor layers;

implanting second impurities into the first or second semiconductor layer; and

performing a second annealing process on the first and second semiconductor layers to remove the metal catalyst remaining in the first or second semiconductor layer having the implanted second impurities,

wherein the first impurities are implanted at a dose of 6×10 13 /cm 2 to 5×10 15 /cm 2 , and the second impurities are implanted at a dose of 1×10 11 /cm 2 to 3×10 15 /cm 2 .

2. The method according to claim 1 , wherein the first impurities are n-type impurities.

3. The method according to claim 2 , wherein the first impurities are elements of group 5 of the periodic table.

4. The method according to claim 2 , wherein the first impurities are one of phosphorus (P), PH x + and/or P 2 H x + where (x=1, 2, 3, . . . ).

5. The method according to claim 2 , wherein the n-type impurities are implanted at an acceleration voltage of 10 keV to 100 keV.

6. The method according to claim 2 , wherein the n-type impurities are implanted so that a projection range (Rp) is within about ±500 Å from an interface between the polysilicon layer and the gate insulating layer.

7. The method according to claim 1 , wherein the first impurities are implanted into source and drain regions of the first and second semiconductor layers.

8. The method according to claim 1 , wherein the second impurities are p-type impurities.

9. The method according to claim 8 , wherein the p-type impurities are one of boron (B), BH x + and/or B 2 H x + where (x=1, 2, 3, . . . ).

10. The method according to claim 9 , wherein the p-type impurities are implanted at an acceleration voltage of 10 keV to 100 keV.

11. The method according to claim 9 , wherein the p-type impurities are implanted so that a projection range (Rp) is within about ±500 Å from an interface between the polysilicon layer and the gate insulating layer.

12. The method according to claim 1 , wherein the second impurities are implanted into source and drain regions of the first or second semiconductor layer.

13. The method according to claim 1 , wherein the second annealing process is performed at a temperature between about 500° C. and about 800° C.

14. The method according to claim 1 , wherein the capping layer is a silicon oxide layer, a silicon nitride layer, or a double layer of a silicon oxide layer and a silicon nitride layer.

15. The method according to claim 1 , wherein the capping layer is formed to a thickness between about 1 and about 2000 Å.

16. The method according to claim 1 , wherein the first semiconductor layer of the first region is a PMOS semiconductor layer and the second semiconductor layer of the second region is an NMOS semiconductor layer.

17. The method according to claim 16 , wherein the second semiconductor layer is formed to have a channel region, a lightly doped drain (LDD) region, and source and drain regions.