PURPOSE: To obtain a TFT having excellent electrical characteristics by a method wherein a lamp light containing a light having a specific wavelength is applied to a specific polycrystalline silicon film into which impurity ions are implanted to activate the impurities.

CONSTITUTION: An amorphous silicon film 102 is deposited on a quartz substrate 101 so as to have a thickness of 1000 and subjected to a lamp annealing with a light having a wavelength not less than 350nm and not larger than 500nm to be converted into a first polycrystalline silicon film. The surface of the polycrystalline silicon film is oxidized to form an SiO2 gate insulating film 103. Then a gate electrode 104 composed of a second polycrystalline silicon film having a thickness of 3500 is formed. Then impurities are introduced in such a manner that phosphorus ions are implanted with a concentration not less than 1×1015/cm3 to form source/drain (105a and 105b) in a self- alignment manner by using the gate electrode 104 as a mask and lamp annealing is performed with a light having a wavelength not less than 350nm and not larger than 500nm to activate the impurities. Then an SiO2 interlayer insulating film 106 is formed and contact holes are drilled and Al wirings 107 are formed.