Silicon-based quantum bits with electron spins in quantum dots or nuclear spins on dopants are serious contenders in the race for quantum computation. Added to process integration maturity, the lack of nuclear spins in the most abundant (28)silicon isotope host crystal for qubits is a major asset for this silicon quantum technology. We have grown (28)silicon epitaxial layers (epilayers) with an isotopic purity greater than 99.992% on 300 mm natural abundance silicon crystals. The quality of the mono-crystalline isotopically purified epilayer conforms to the same drastic quality requirements as the natural epilayers used in our pre-industrial CMOS facility. The isotopically purified substrates are now ready for the fabrication of silicon qubits using state-of-the-art 300 mm Si CMOS-foundries equipments and processes.