PURPOSE: To exclude the overlapping parts between electrodes of a base, a source, and a drain, and reduce capacitances between the electrodes, by diffusing impurities by the effect of temperature rise of a semiconductor layer caused by projecting laser light from the substrate side while using a gate electrode as a mask.

CONSTITUTION: A gate insulating film 4, a semiconductor layer 3, a impurity containing layer 7 are formed in order on a gate electrode 2 on a substrate 1. From the substrate 1 side, laser light 11 is projected; the impurities in the layer 7 are diffused in the semiconductor layer 3 by the effect of temperature rise in the layer 3, thereby forming a source.drain region, on which a source electrode 5 and a drain electrode 6 are formed. The temperature rise caused by the laser light 11 is restricted within a region which does not overlap at all with the gate electrode 2 irradiated with the laser light 11 while the gate electrode 2 is used as a mask, so that overlapping parts between the gate electrode and the source and the drain electrodes are not generated. Thereby capacitances between electrodes are reduced, and the rise time characteristics of a gate signal can be improved.