This invention relates to a method of processing a substrate, having on one side a device area with a plurality of devices. The method includes attaching a first protective film to the one side of the substrate, so that at least a central area of a front surface of the first protective film is in direct contact with the one side of the substrate, and attaching a second protective film to the opposite side of the substrate. After attaching the second protective film, a laser beam is applied to the substrate from the opposite side of the substrate. The substrate and second protective film are transparent to the laser beam. The laser beam is applied to the substrate in a plurality of positions so as to form a plurality of modified regions in the substrate.