Abstract: A laser processing method includes: a forming step of forming a plurality of modified spots along an imaginary plane inside a work piece by irradiating an inside of the work piece with laser light from a surface. The work piece includes a first region and second region when viewed in a direction perpendicular to the surface. In the forming step, a plurality of modified spot rows formed of the plurality of modified spots arranged along a boundary between the first region and the second region are formed in the second region, the plurality of modified spot rows being arranged along a direction intersecting an arrangement direction of the plurality of modified spots, and a crack extending from the second region to the first region is formed by forming the plurality of modified spot rows.

Abstract: A manufacturing method of a semiconductor device, includes: forming a gas vent recess in a first surface of a compound semiconductor substrate, which includes a plurality of device regions adjacent to the first surface, along an interface between the plurality of device regions; forming an altered layer inside the compound semiconductor substrate to extend along the first surface at a depth corresponding to a range of a depth of the gas vent recess by applying a laser beam; dividing the compound semiconductor substrate at the altered layer into a first part including the first surface and a second part including a second surface of the compound semiconductor substrate opposite to the first surface; and forming a metal film to cover a divided surface of the first part while exposing the gas vent recess.