Oxide thin film transistor and manufacturing method thereof, array substrate and display device

A manufacturing method of an oxide thin film transistor, comprising:

• forming a gate electrode and a gate insulating layer sequentially on a substrate;
• forming an oxide semiconductor thin film on the gate insulating layer, and forming a first photoresist above an active layer region of the oxide semiconductor thin film, wherein a thickness of a portion of the first photoresist above a channel region is greater than a thickness of a portion of the first photoresist above a non-channel region;
• removing a non-active layer region of the oxide semiconductor thin film to form a pattern of an active layer, removing the portion of the first photoresist above the non-channel region, and reserving the portion of the first photoresist above the channel region;
• forming a source-drain metal thin film and a second photoresist sequentially on the pattern of the active layer, removing part of a portion of the source-drain metal thin film corresponding to the portion of the first photoresist above the channel region and part of a portion of the second photoresist corresponding to the portion of the first photoresist above the channel region, such that an edge of the portion of the first photoresist above the channel region is covered by a portion of the remaining source-drain metal thin film;
• and
• lifting off the remaining second photoresist, removing the portion of the remaining source-drain metal thin film covering the edge of the portion of the first photoresist above the channel region, and lifting off the portion of the first photoresist above the channel region to form patterns of a source electrode and a drain electrode.