Thin film transistor, manufacturing method therefor, array substrate and display device

A method for manufacturing a thin film transistor, comprising:

• forming a buffer layer on a base substrate;
• forming a source electrode and a drain electrode on a base substrate the buffer layer, the buffer layer is between the base substrate and the source electrode and between the base substrate and the drain electrode;
• forming a photoresist layer on a side of the source electrode and the drain electrode away from the base substrate;
• exposing and developing the photoresist layer to form a photoresist pattern;
• forming a semiconductor layer, a first insulation layer and a conductive layer successively on a side of the photoresist pattern away from the base substrate;
• and
• removing the photoresist pattern to form an active layer, a gate insulation layer and a gate electrode,
• wherein the photoresist layer is exposed to an UV light, the UV light comes from a side of the base substrate away from the photoresist layer and passes through the base substrate and the buffer layer to irradiate the photoresist layer,
• where the source electrode and the drain electrode serve as a mask for exposing the photoresist layer so as to form the photoresist pattern, such that the photoresist pattern has a same pattern as those of the source electrode and the drain electrode, and the mask is only one mask for forming the photoresist pattern,
• wherein after removing the photoresist pattern to form the active layer, the gate insulation layer and the gate electrode, the method further comprises:
• forming a second insulation layer on one side of the source electrode and the drain electrode away from the base substrate,
• wherein the second insulation layer overlays the source electrode, the drain electrode and the gate electrode, and the second insulation layer has a planar surface.