Provided are a poly crystalline silicon semiconductor device and a method of fabricating the same. Portions of a silicon layer except for gates are removed to reduce a parasitic capacitance caused from the silicon layer existing on gate bus lines. The silicon layer exists under the gates only, thus the parasitic capacitance is reduced and the deterioration and the delay of signals are prevented. Accordingly, the poly crystalline silicon semiconductor device, such as a thin film transistor, has excellent electric characteristics.