COMPOSITE SEMICONDUCTOR SUBSTRATE

PROBLEM TO BE SOLVED: To provide a composite semiconductor substrate which is small in warp even in case of large wafer diameter. SOLUTION: In a composite semiconductor substrate where one or more pieces, separated from one another, of single-crystal semiconductor regions 11 and a supporting substrate 14 supporting them are directly joined with one another through the layer 17 consisting of a polycrystalline or amorphous semiconductor, the bottom or the flank of the single-crystal semiconductor region 11 are covered with an insulating film 12, and further a warp correcting layer 15 and a cover layer 16 to cover the warp correcting layer 15 are provided at the rear of the supporting substrate.