PURPOSE: To improve the throughput and controllability when amorphous silicon semiconductor layers and polycrystalline silicon semiconductor layers are formed on the same substrate.

CONSTITUTION: A polycrystalline silicon semiconductor layer 11 is formed on the upper surface of a substrate 1 and a gate insulating film 5 is formed on the upper surface of the layer 11. A photoresist pattern 13 is formed on the upper surface of the gate insulating film 5. If silicon ions are implanted with the photoresist pattern 13 as a mask, the parts of the polycrystalline silicon layer 11 into which the silicon ions are implanted are converted into amorphous silicon semiconductor layers 14. At that time, the silicon ions can be implanted into the required regions simultaneously and, further, the implantation regions can be controlled by the photoresist pattern 13, so that the throughput and controllability can be improved.