Thin film transistor and manufacturing method thereof as well as array substrate, display panel and display device

The invention discloses a thin film transistor and a manufacturing method thereof as well as an array substrate, a display panel and a display device, aiming at increasing the width to length ratio of the thin film transistor and improving the aperture opening ratio. The thin film transistor comprises a substrate, a grid electrode arranged on the substrate, a grid electrode insulation layer, a semiconductor active layer, a source electrode and a drain electrode, wherein the substrate is provided with a bulge, and the position of the bulge corresponds to that of the semiconductor active layer to be manufactured.