Embodiments of the disclosed technology disclose manufacture methods of a thin film transistor and an array substrate and a mask therefor are provided. The manufacture method of the thin film transistor comprises: patterning a wire layer by using a exposure machine and a mask with a first exposure amount larger than a normal exposure amount during formation of source and drain electrodes; forming a semiconductor layer on the patterned wire layer; patterning the semiconductor layer by using the exposure machine and the mask with a second exposure amount smaller than the first exposure amount. The mask comprises a source region for forming the source electrode, a drain region for forming the drain electrode and a slit provided between the source region and the drain region, and the width of the slit is smaller than the resolution of the exposure machine.