A thin-film transistor (TFT) comprises a gate electrode, a gate insulating layer, a source electrode and a drain electrode which are formed on a base substrate, the source electrode and the drain electrode are disposed on different layers and isolated from each other through a semiconductor connecting section made of an oxide semiconductor material; a position of the semiconductor connecting section corresponds to a position of the gate electrode; and at least one part of the source electrode and at least one part of the drain electrode overlap each other at a position corresponding to the semiconductor connecting section. A display device comprising the TFT and a display device comprising the display device are also disclosed.