Composite substrate and production method therefor

A method for producing a composite substrate having a silicon wafer, an interlayer, and an oxide single-crystal thin film stacked in the order listed, comprising the steps of:

• forming the interlayer on a surface of the silicon wafer;
• subjecting a side of the interlayer of the silicon wafer to ion implantation treatment and then to thermal treatment at a temperature of 400° C. to 600° C. to form a damaged layer in a portion of the silicon wafer on the side of the interlayer;
• bonding the silicon wafer and an oxide single-crystal wafer to each other with the interlayer therebetween to obtain a laminate;
• and
• thinning the oxide single-crystal wafer of the laminate into the oxide crystal thin film,
• wherein ion species to be implanted by the ion implantation treatment are hydrogen atom ions (H+) at a dose between 2.5×1016 and 5.0×1016 atoms/cm2 or hydrogen molecule ions (H2+) at a dose between 1.25×1016 and 2.5×1016 atoms/cm2.