Thin film transistor substrate and method for manufacturing the same and organic light emitting device using the same

A method for manufacturing a thin film transistor substrate comprising:

• sequentially forming a lower gate electrode of a thin film transistor of an organic light emitting device (OLED) pixel, a gate insulating layer, and an active layer on a substrate;
• forming a first contact hole by patterning the gate insulating layer to expose the lower gate electrode;
• forming a source/drain electrode layer on the active layer;
• forming a source electrode of the thin film transistor of the OLED pixel, a drain electrode of the thin film transistor of the OLED pixel, and a contact portion by patterning the source/drain electrode layer, wherein the contact portion is brought into contact with the lower gate electrode through the first contact hole;
• forming a passivation layer on an entire surface of the substrate including the source electrode, drain electrode, and contact portion;
• forming a second contact hole by patterning the passivation layer to expose the contact portion;
• and
• forming an upper gate electrode on the passivation layer, wherein the upper gate electrode covers a channel region defined by the source electrode and the drain electrode, and the upper gate electrode is brought into contact with the contact portion through the second contact hole.