PURPOSE: To obtain a semiconductor medim for recording enabling a high readout speed, by forming a dead band through the radiation of charged particle rays to the specified position on a semiconductor substrate and recording the information according to the presence of this dead band.

CONSTITUTION: The semiconductor substrate 2 is single conduction type, has not junction, and electrodes 8" and 8''' are fitted to the both sides of the substrate front. When a current is fed through the bias resistor 9 from the bias power supply 7 via the electrodes 8" and 8''', the change in the electric conductivity in the semiconductor substrate 2 by the radiation of electron rays is read out at the amplifier 10. In forming dead bands 5, 5', the beam having the intensity of 1/109W1/1010 A of Ar ions accelerated by 60kV is used. By the ion beam like this, the spot diameter of 0.1μm can be obtained, allowing to achieve the recording with high density.