Channel-etch thin film transistor

1. A channel-etch thin film transistor including:

a gate electrode over a substrate;

a gate insulation film extending over said gate electrode and said substrate;

an active layer including a channel region over said gate insulation film;

source and drain regions on said active layer;

a source electrode connected with said source region, and said source electrode including a source electrode primary portion in contact with said source region and a source electrode lead portion extending from said source electrode primary portion; and

a drain electrode connected with said drain region, and said drain electrode including a drain electrode primary portion in contact with said drain region and a drain electrode lead portion extending from said drain electrode primary portion,

wherein at least one of said source electrode lead portion and said drain electrode lead portion has a side-contact portion in contact directly with a side wall of said active layer, and an averaged width of said side-contact portion is narrower than an averaged width of corresponding one of said source electrode primary portion and said drain electrode primary portion.

2. The channel-etch thin film transistor as claimed in claim 1 , wherein each of said source electrode lead portion and said drain electrode lead portion has said side-contact portion in contact directly with said side wall of said active layer, and said averaged width of said side-contact portion is narrower than said averaged width of each of said source electrode primary portion and said drain electrode primary portion.

3. The channel-etch thin film transistor as claimed in claim 1 , wherein a peripheral edge of said gate electrode is positioned outside of a peripheral edge of said active layer in plan view.

4. The channel-etch thin film transistor as claimed in claim 1 , wherein said substrate comprises a glass substrate of a liquid crystal display, and said source electrode is connected to a pixel electrode, and said drain electrode is connected to a data line.

5. The channel-etch thin film transistor as claimed in claim 1 , wherein said side-contact portion is narrower in width than an end portion of said corresponding one of said source electrode primary portion and said drain electrode primary portion, and said end portion confronts counterpart one of said source electrode primary portion and said drain electrode primary portion.

6. The channel-etch thin film transistor as claimed in claim 5 , wherein at least one of said source electrode primary portion and said drain electrode primary portion has a wide region which has the same width as said end portion and a length of at least 3 micrometers along a channel length direction.

7. The channel-etch thin film transistor as claimed in claim 1 , wherein said source electrode primary portion and said drain electrode primary portion are symmetrical in view of plan view.

8. The channel-etch thin film transistor as claimed in claim 7 , wherein both of said source electrode lead portion and said drain electrode lead portion have side-contact portions in contact directly with said side walls of said active layer, and each of said side-contact portions is narrower than each of said source electrode primary portion and said drain electrode primary portion.

9. The channel-etch thin film transistor as claimed in claim 1 , wherein said source electrode primary portion and said drain electrode primary portion are asymmetrical in view of plan view.

10. The channel-etch thin film transistor as claimed in claim 9 , wherein said drain electrode lead portion has a side-contact portion in contact directly with said side wall of said active layer, said side-contact portion of said drain electrode lead portion is narrower than said drain electrode primary portion, and said source electrode primary portion is narrower than said drain electrode primary portion, and said source electrode lead portion has another side-contact portion having a width narrower than or equal to said source electrode primary portion.