A composite substrate (1) comprising a substrate body (2) and a utility layer (31) fixed on the substrate body (2). A planarization layer (4) is arranged between the utility layer (31) and the substrate body (2). A method for producing a composite substrate (1) applies a planarization layer (4) on a provided utility substrate (3). The utility substrate (3) is fixed on a substrate body (2) for the composite substrate (1). The utility substrate (3) is subsequently separated, wherein a utility layer (31) of the utility substrate (3) remains for the composite substrate (1) on the substrate body (2).