Method for manufacturing thin film transistor and thin film transistor

A method for manufacturing a thin film transistor, comprising:

• providing a substrate;
• forming an active layer on the substrate and patterning the active layer, wherein the active layer is made of cubic boron nitride and the patterned active layer comprises a channel region and doped regions disposed at two sides of the channel region;
• applying a doping process to the patterned active layer;
• forming a first insulating layer upon the substrate;
• forming a gate electrode metal layer upon the substrate;
• forming a second insulating layer upon the substrate;
• and
• forming a source and drain metal layer upon the substrate;
• wherein during the step of forming an active layer on the substrate, the active layer is formed by a chemical vapor deposition method, vapor for forming the active layer comprise boron chloride, boron hydride, and ammonia;
• wherein the step of forming the active layer on the substrate comprises:
• coating a photoresist on the active layer;
• exposing and developing the photoresist by a mask process to form an exposing region to expose the active layer;
• etching the active layer disposed in the exposing region to form a patterned active layer;
• and
• removing a remaining part of the photoresist;
• wherein the step of applying the doping process to the patterned active layer comprises:
• applying a first doping treatment to the doping regions;
• forming the first insulating layer on the patterned active layer;
• forming through holes in the first insulating layer corresponding to the doping regions to expose at least a part of the doping regions;
• and
• applying a second doping treatment to the doping regions exposed by the through holes, wherein a doping amount of an element of the second doping treatment is less than one third of a doping amount of an element of the first doping treatment.