Thin film transistor and method for manufacturing the same, display panel and method for manufacturing the same

A method for manufacturing a thin film transistor, comprising:

• providing a substrate;
• forming a gate electrode and a first electrode in a single layer on the substrate by a patterning process;
• forming an active layer above the first electrode, an orthographic projection of the active layer on the substrate at least partially covers an orthographic projection of the first electrode on the substrate;
• forming a first insulation layer covering the gate electrode, the first electrode, the active layer, a portion of the substrate exposed between the gate electrode and the active layer, and another portion of the substrate exposed between the gate electrode and the first electrode;
• and
• forming a second electrode on the first insulation layer, an orthographic projection of the second electrode on the substrate at least partially covers the orthographic projection of the active layer on the substrate, and the second electrode is connected to the active layer through a via-hole in the first insulation layer,
• wherein the orthographic projection of the second electrode on the substrate at least partially cover the orthographic projection of the first electrode on the substrate, a portion of the active layer between the first electrode and the second electrode is flat and functions as a channel of the thin film transistor, and a length of the channel equals to a thickness of the active layer between the first electrode and the second electrode in a direction perpendicular to the substrate.