a non single crystalline semiconductor layer on an insulating surface forming a gate electrode on the semiconductor layer with a gate insulating layer formed therebetween doping portions of the semiconductor layer with an impurity to form source and drain regions and exposing the doped portions with light to crystallize the portions and activate the dopant since the gate electrode extends beyond the edges of the gate electrode the doping of the portions of the semiconductor layer and the exposure to light irradiation is carried out through a part of the gate insulating layer application_number US 17176993 A description fig1 3 and 4 illustrate first second third and fourth embodiments of the present invention respectively in which an island shaped n u2212 p u2212 or i type non single crystal semiconductor layer 2 is formed for example 0 7 u03bcm on for example a 1 1 mm thick insulating substrate 1 as of quartz glass the non single crystal semiconductor layer 2 is constituted of for instance amorphous microcrystalline or polycrystalline silicon the non single crystal semiconductor layer 2 is doped with a hydrogen or a halogen such as fluorine as a recombination center neutralizer in an amount of 1 atom or more the non single crystal semiconductor layer 2 is deposited over the entire.