150 mm Silicon-on-polycrystallin-Silicon Carbie (poly-SiC) bybrid substrate, without intermediate oxide layers have been realised by hydrophilic wafer bonding of SOI- and poly-SiC wafers. A novel rapid thermal treatment step was introduced before furnace annealing to avoid bubble formation, cracks and breakage. After removal of the Si handle and the buried oxide, the reamining Si device layer was shown to be stress free by Raman spectroscopy and X-ray diffraction (XRD) measurements.