US Patent 7943414 Method for manufacturing SOI substrate

An object of an embodiment of the present invention to be disclosed is to prevent oxygen from being taken in a single crystal semiconductor layer in laser irradiation even when crystallinity of the single crystal semiconductor layer is repaired by irradiation with a laser beam; and to make substantially equal or reduce an oxygen concentration in the semiconductor layer after the laser irradiation comparing before the laser irradiation. A single crystal semiconductor layer which is provided over a base substrate by bonding is irradiated with a laser beam, whereby the crystallinity of the single crystal semiconductor layer is repaired. The laser irradiation is performed under a reducing atmosphere or an inert atmosphere.