Embodiments of the present invention disclose a low temperature poly-silicon thin film transistor and a method of fabricating the same, an array substrate, and a display device. The low temperature poly-silicon thin film transistor comprises an active layer, a source and a drain, wherein the active layer comprises a source contact region, a drain contact region, and a channel region located between the source contact region and the drain contact region, the source is provided above and connected to the source contact region, the drain being provided above and connected to the drain contact region, and thicknesses of the source contact region and the drain contact region are both larger than that of the channel region.