The present disclosure provides a method for manufacturing a thin film transistor, a thin film transistor, and a display apparatus. The method for manufacturing a thin film transistor includes: forming a gate layer on a substrate; forming a gate insulating layer on the gate layer; forming an active layer on the gate insulating layer; forming a source/drain layer on the active layer; and performing a plasma bombardment treatment on a surface of the active layer on which the source/drain layer is formed, and controlling the plasma bombardment treatment to be performed at a gas flow rate of 4K sccm to 70K sccm, at a pressure of 600 mTorr to 1200 mTorr, at a power of 4 KW to 12 KW for a treatment time of 10 s to 60 s.