Disclosed is a thin film semiconductor device for a display device. The thin film semiconductor device is provided with: a first channel layer (130), which is composed of a polycrystalline semiconductor layer; a second channel layer (140), which is composed of an amorphous semiconductor layer formed on the first channel layer (130), and which has a protruding portion on the surface; an insulating layer (150), which is formed on the upper surface of the protruding portion of the second channel layer (140); contact layers (160, 161), which are respectively formed on the upper surfaces and the side surfaces of the end portions of the insulating layer (150), the side surfaces of the protruding portion of the second channel layer (140), said side surfaces being continuous to the side surfaces of the insulating layer (150), and the upper surfaces of the second channel layer (140), said upper surfaces being continuous to the side surfaces of the protruding portion of the second channel layer (140); and a source electrode (170) and a drain electrode (171). The contact layers (160, 161) are first conductivity type, and the upper portion of the protruding portion of the second channel layer (140) is second conductivity type, in such a way that an off-current is significantly reduced, while significantly increasing an on-current.