PURPOSE: To obtain a semiconductor device having high reliability by preventing the electrostatic breakage of an insulating film by increasing the generation quantity of electrons in plasma by using an electron generating means, pulling out electrons by the positive potential generated on a semiconductor substrate, and neutralizing the semiconductor substrate which is electrified by the ion injection.

CONSTITUTION: An electric charge neutralizing device 14A as electron generating means is installed in proximity to a semi-conductor substrate 7 by a thermal electron discharge type plasma source. The electric charge neutralizing device 14A is constituted of a filament 19, arc chamber 20, and a gas introducing pipe 21, and the generation of the high density plasma is enabled. The semiconductor substrate 7 which is electrified by the radiation of ion beams 3 pulls out electrons from the electric charge neutralizing device 14A by the own positive potential when passing through the electric charge neutralizing device 14A, and softens the positive electrification.