Hydrogen ions are implanted to a surface (main surface) of the single crystal Si substrate 10 to form the hydrogen ion implanted layer (ion-implanted damage layer) 11. As a result of the hydrogen ion implantation, the hydrogen ion implanted boundary 12 is formed. The single crystal Si substrate 10 is bonded to the quartz substrate 20 having a carbon concentration of 100 ppm or higher, and an external shock is applied near the ion-implanted damage layer 11 to delaminate the Si crystal film along the hydrogen ion implanted boundary 12 of the single crystal Si substrate 10 out of the bonded substrate. Then, the surface of the resultant silicon thin film 13 is polished to remove a damaged portion, so that an SOQ substrate can be fabricated. There can be provided an SOQ substrate highly adaptable to a semiconductor device manufacturing process.