There are disclosed a method for producing an SOI substrate comprising forming an oxide layer on a surface of at least one silicon wafer among two silicon wafers, closely contacting one wafer with the other wafer so that the oxide layer should be interposed between them, subjecting the wafers to a heat treatment to firmly bond the wafers, and making a device processing side wafer thinner to a desired thickness, wherein a silicon single crystal wafer obtained by growing a silicon single crystal ingot doped with nitrogen by the Czochralski method, and slicing the single crystal ingot into a silicon single crystal wafer is used as the device processing side wafer, and an SOI substrate produced by the method. The present invention provides a method for producing SOI substrates, in particular thin film SOI substrates having an SOI layer thickness of 1 &mgr;m or less, exhibiting a small crystal defect size in the SOI layer, and SOI substrates with low cost and high productivity.