A method of manufacturing a semiconductor device includes steps of forming a gate electrode over a light-transmitting substrate, forming a gate insulating layer containing an inorganic material over the gate electrode and the substrate, forming an organic layer containing a photopolymerizable reactive group over the gate insulating layer, polymerizing selectively the organic layer by irradiating the organic layer with light from back side of the substrate, using the gate electrode as a mask, forming an organic polymer layer by removing a residue of the organic layer, being other than polymerized, forming an organosilane film including a hydrolytic group over the gate insulating layer in a region other than a region in which the organic polymer layer is formed, forming source and drain electrodes by applying a composition containing a conductive material over the organic polymer layer, and forming a semiconductor layer over the gate electrode, the source and drain electrodes.