The invention provides a thin film transistor having current driving force that can be substantially improved. By heat treatment, the IGZO layer (45) from which oxygen is taken away by the titanium electrodes (65) becomes the low resistance regions (40b), and the IGZO layer (45) from which oxygen is not taken away remains as the high resistance region (40a). In this state, when the gate voltage is applied to the gate electrode (20), electrons in the low resistance regions (40b) near the boundaries with the high resistance region (40a) move respectively to the titanium electrode (65) sides. As a result, the length of the low resistance regions (40b) becomes short, and oppositely, the length of the high resistance region (40a) becomes longer by the size of the shortened low resistance regions. However, the electrical channel length (Le) becomes shorter than the source/drain interval space (Lch) as the limit resolution of the exposure device, and the current driving force becomes large.