PURPOSE: To provide a semiconductor substrate with linear damage isotropically and to make its warp avoidable, by installing a mechanism in a gettering device so that it can be moved vertically and horizontally and rotated.

CONSTITUTION: A semiconductor substrate 3 is fixed. A susceptor 4 is mounted on a rotary structure part 5. The structure 5 is installed on a horizontal moving mechanism 6. The mechanism 6 is installed in a vertical moving mechanism 7. The mechanism 7 is installed in a forward/backward moving mechanism 8. The mechanisms 6, 7 are used to move a center of the substrate so that it comes at a right end of laser beams, and next the substrate is rotated at an 0.3rps by the rotary structure part 5 to be irradiated with 200Hz laser beams of Excimer laser 1. Subsequently the center of the 3cm substrate is moved rightward and then it is rotated at an 0.15rps and irradiated with the laser beams. The whole rear side of the substrate is thus provided with spiral damage at intervals of 30μm or less. Also a warp of the substrate can be suppressed to be 0.5μm or less.