An integration method of fabricating optical sensor device and thin film transistor device includes the follow steps. A substrate is provided, and a gate electrode and a bottom electrode are formed on the substrate. A first insulating layer is formed on the gate electrode and the bottom electrode, and the first insulating layer at least partially exposes the bottom electrode. An optical sensing pattern is formed on the bottom electrode. A patterned transparent semiconductor layer is formed on the first insulating layer, wherein the patterned transparent semiconductor layer includes a first transparent semiconductor pattern covering the gate electrode, and a second transparent semiconductor pattern covering the optical sensing pattern. A source electrode and a drain electrode are formed on the first transparent semiconductor pattern. A modification process including introducing at least one gas is performed on the second transparent semiconductor pattern to transfer the second transparent semiconductor pattern into a conductive transparent top electrode.