A manufacturing method of the present invention includes a process using a first multi-tone mask, in which a first conductive layer in which a transparent conductive layer and a metal layer are stacked over a substrate, a gate electrode formed of a first conductive layer, and a pixel electrode formed of a single layer of the transparent conductive layer are formed, a process using a second multi-tone mask, in which a contact hole to the pixel electrode, and an island of an i-type semiconductor layer and an n+ type semiconductor layer are formed after a gate insulating film, the i-type semiconductor layer, and the n+ type semiconductor layer are formed, a process using a third photomask, in which a source electrode and a drain electrode are formed after a second conductive layer is formed, and a process using a fourth photomask, in which an opening region is formed after a protective film is deposited.