A thin film transistor and a method for manufacturing the same, an array substrate, and a display device are provided in embodiments of the disclosure. The method for manufacturing a thin film transistor in embodiments of the disclosure forms a plurality of strip-shaped protrusions on a substrate by a patterning process before forming structures of various layers of the thin film transistor, and then forms sequentially a gate electrode, a gate insulating layer, an active layer, a source-drain electrode on the plurality of strip-shaped protrusions; in other words, the thin film transistor is prepared, whose channels are aligned with and shaped to be similar to the plurality of strip-shaped protrusions, in a widthwise direction thereof.