THIN FILM TRANSISTOR AND MANUFACTURING METHOD THEREOF, DISPLAY SUBSTRATE AND DISPLAY DEVICE

A thin film transistor having a groove structure with an increased width-to-length ratio, manufacturing method thereof, and display substrate and display device comprising the thin film transistor. The thin film transistor comprises a gate electrode (110), a gate insulating layer (120) and an active layer (130) stacked on a base substrate (100); the active layer (130) is formed with a source electrode region, a drain electrode region and a groove region; at least a part of a surface of the active layer (130) facing toward the gate insulating layer (120) is a non-planar surface in the groove region, such that the non-planar surface of the active layer (130) has a zigzag shape in a width direction of the groove region.