Thin film transistor and fabrication method thereof, array substrate and fabrication method thereof, and display panel

A method for fabricating a thin film transistor, comprising:

• forming an active layer on a substrate, the active layer comprising a first region, a second region, and a third region;
• forming a gate insulating layer on a side of the active layer away from the substrate;
• forming a gate electrode on a side of the gate insulating layer away from the active layer, wherein an orthographic projection of the first region of the active layer on the substrate does not overlap with an orthographic projection of the gate insulating layer on the substrate and an orthographic projection of the gate electrode on the substrate, an orthographic projection of the second region of the active layer on the substrate overlaps with the orthographic projection of the gate insulating layer on the substrate but does not overlap with the orthographic projection of the gate electrode on the substrate, and an orthographic projection of the third region of the active layer on the substrate overlaps with both the orthographic projection of the gate insulating layer on the substrate and the orthographic projection of the gate electrode on the substrate;
• and performing ion implantation on the active layer from a side of the gate electrode away from the active layer, so that the first region of the active layer is formed into a heavily doped region, the second region of the active layer is formed into a lightly doped region, and the third region of the active layer is formed into an active region;
• wherein forming the gate insulating layer further comprises forming a plurality of through holes penetrating the gate insulating layer in a region of the gate insulating layer not overlapping with the gate electrode in a direction perpendicular to the substrate, and the plurality of through holes have an aperture in a range of 1 to 4 μm.