PURPOSE: To increase an etching speed, to enhance the selectivity of an etching region and to make an element minute and highly reliable by a method wherein a strong laser beam is condensed to an optical scatterer on a wafer by utilizing an amplification and phase conjugate reflection system and a pretreatment and a selective etching operation are executed.

CONSTITUTION: A primary scattered beam 7 of a laser is incident on amplification and phase conjugate reflection systems 1W4 by means of a mirror 5, an incident beam is amplified by the amplifier 2 and reflected by the phase conjugate mirror 1, an amplification and phase conjugate reflected beam 8 which has been amplified and time-reversed by means of the amplifier 2 is incident on a wafer 6 via the mirror 5 and, the wafer is pretreated and etched. Since a completely conjugate reflected wave traces the completely same route as the incident beam, a strain of a wave front due to a medium in a halfway part is removed completely and the wave front is returned accurately to an original pattern, a signal strain of an optical transmission line can be removed and a strong laser beam can be applied to a minute fuel element (optical scatterer) of laser nuclear fusion. By this setup, etching speed can be increased, the selectivity of etching region can be enhanced and an element can be made minute and highly reliable.