Thin film transistor substrate and method for fabricating same

1 . A thin film transistor substrate, comprising:

a base;

a semiconductor pattern formed on the base, the semiconductor pattern comprising a heavily doped polysilicon pattern and a lightly doped polysilicon pattern;

a first gate insulating layer formed on the semiconductor pattern; and

a gate electrode and a common capacitor electrode formed on the first gate insulating layer;

wherein the gate electrode and the common capacitor electrode correspond to the lightly doped polysilicon pattern.

2 . The thin film transistor substrate of claim 1 , further comprising a first capacitor, wherein the first capacitor comprises a first electrode, and the first electrode is part of the lightly doped polysilicon pattern corresponding to the common capacitor electrode.

3 . The thin film transistor substrate of claim 2 , further comprising a second gate insulating layer, wherein the second gate insulating layer is formed on the gate electrode, the common capacitor electrode, and the first gate insulating layer.

4 . The thin film transistor substrate of claim 3 , further comprising a drain electrode, a source electrode, a gate contact portioncontact portion, and a capacitor contact portioncontact portion, wherein the drain electrode, the source electrode, the gate contact portioncontact portion, and the capacitor contact portioncontact portion are formed on the second gate insulating layer.

5 . The thin film transistor substrate of claim 4 , wherein the capacitor contact portioncontact portion is connected to the first electrode via a capacitor contact holecontact hole in the first and second gate insulating layers.

6 . The thin film transistor substrate of claim 5 , wherein the drain electrode and the source electrode are connected to the semiconductor pattern via a drain contact holecontact hole and a source conducting hole in the first and second gate insulating layers respectively, and the gate contact portioncontact portion is connected to the gate electrode via a gate contact holecontact hole in the second gate insulating layer.

7 . The thin film transistor substrate of claim 6 , further comprising a passivation layer, wherein the passivation layer is formed on the drain electrode, the source electrode, the gate contact portioncontact portion, the capacitor contact portioncontact portion, and the second gate inslulating layer.

8 . The thin film transistor substrate of claim 7 , further comprising a transparent contact pattern, wherein the transparent contact pattern is formed on the passivation layer, the transparent contact pattern comprises a pixel electrode and a second electrode, the pixel electrode is connected to the drain electrode via a first contact holecontact hole in the passivation layer, and the second electrode is connected to the capacitor contact portioncontact portion via a second transparent contact pattern.

9 . The thin film transistor substrate of claim 8 , further comprising a second capacitor, wherein the second capacitor is connected parallel to the first capacitor, and the second electrode and the common capacitor electrode are two electrodes of the second capacitor.

10 . The thin film transistor substrate of claim 9 , further comprising a plurality of gate lines, wherein the gate electrode and the common capacitor electrode are connected to two adjacent gate lines, respectively.

11 . A method for fabricating a thin film transistor substrate, the method comprising:

providing a base;

forming a polysilicon pattern on the base in a first photo-mask process;

forming a first gate insulating layer on the polysilicon pattern;

forming a gate electrode and a common capacitor electrode on the first gate insulating layer in a second photo-mask process; and

forming a heavily doped polysilicon pattern and a lightly doped polysilicon pattern by doping the polysilicon pattern using the gate electrode and the common capacitor electrode as a mask;

wherein the gate electrode and the common capacitor electrode correspond to the lightly doped polysilicon pattern.

12 . The method of claim 11 , further comprising: forming a second gate insulating layer on the gate electrode, the common capacitor electrode, and the first gate insulating layer; and forming a source contact holecontact hole, a drain contact holecontact hole, a gate contact holecontact hole, and a capacitor contact holecontact hole in a third photo-mask process.

13 . The method of claim 12 , further comprising: forming a source electrode, a drain electrode, a gate contact portioncontact portion, and a capacitor contact portioncontact portion on the second gate insulating layer in a fourth photo-mask process.

14 . The method of claim 13 , further comprising: forming a passivation layer on the source electrode, the drain electrode, the gate contact portioncontact portion, the capacitor contact portioncontact portion, and the second gate insulating layer; and forming a first contact hole and a second contact hole in the passivation layer in a fifth photo-mask process.

15 . The method of claim 14 , further comprising: forming a transparent contact pattern on the passivation layer in a fifth photo-mask process.

16 . The method of claim 11 , further comprising: forming a P-type semiconductor pattern by doping the polysilicon pattern, before forming the first gate insulating layer.