A manufacturing method of a thin film transistor is provided. An insulating pattern layer having at least one protrusion is formed on a substrate. At least one spacer and a plurality of amorphous semiconductor patterns separated from each other are formed on the insulating pattern layer. The spacer is formed at one side of the protrusion and connected between the amorphous semiconductor patterns. The spacer and the amorphous semiconductor patterns are crystallized. The protrusion and the insulating pattern layer below the spacer are removed so that a beam structure having a plurality of corners is formed and suspended over the substrate. A carrier tunneling layer, a carrier trapping layer and a carrier blocking layer are sequentially formed to compliantly wrap the corners of the beam structure. Hereafter, a gate is formed on the substrate to cover the beam structure and wrap the carrier blocking layer.