Thin film transistor and photoelectric device thereof

A thin film transistor, comprising:

• a gate electrode, disposed on a substrate;
• a semiconductor layer, disposed on the substrate, wherein the semiconductor layer overlaps with the gate electrode;
• a gate dielectric layer, disposed between the gate electrode and the semiconductor layer, wherein a vertical projection scope of the gate dielectric layer on the substrate is substantially a same as a vertical projection scope of the semiconductor layer on the substrate;
• a first dielectric layer, disposed on the substrate, wherein the first dielectric layer covers two sides of the gate electrode or the semiconductor layer and is in contact with two sides of the gate dielectric layer or two sides of the semiconductor layer, a dielectric constant of the first dielectric layer is less than a dielectric constant of the gate dielectric layer, and the dielectric constant of the first dielectric layer is less than 4 and greater than 0;
• and
• a source electrode and a drain electrode, disposed on the substrate, wherein the source electrode is separated from the drain electrode, and the source electrode and the drain electrode separately contact the semiconductor layer.