Abstract: The invention provides a display device and a method of manufacturing a thin film transistor. The method of manufacturing a thin film transistor comprises: (A) providing a substrate; (B) forming a light shielding layer on the substrate, and patterning the light shielding layer to form a patterned light shielding layer; (C) forming a buffer layer on the substrate; (D) forming a semiconductor layer on the substrate, and patterning the semiconductor layer to form a patterned semiconductor layer; (E) forming an insulating layer on the substrate; and (F) forming a conductive layer on the substrate, and patterning the conductive layer to form a patterned conductive layer; wherein the same mask is used for patterning the light shielding layer and the semiconductor layer. Photoelectric effect of the thin film transistor outside the display region can be effectively avoided, while reducing the number of masks in the production process.