A method of manufacturing a display device includes forming a buffer layer on a top surface of a substrate, forming an amorphous silicon layer on a top surface of the buffer layer, and forming a polysilicon layer by irradiating the amorphous silicon layer with a laser beam. A plurality of first protrusions are formed on the top surface of the polysilicon layer, and a plurality of second protrusions are formed on a surface of the buffer layer by transferring the shape of the polysilicon layer to the buffer layer. A gate insulator on the buffer layer is then formed in the shape of bumps of the second protrusions.