We are growing at CEA (i) high purity 28 Si layers and (ii) c-Ge/SiGe heterostructures for electron and hole spin quantum bits. We describe here strategies usable for the fabrication of 28 SOI substrates, with a focus on 28 SiH 4 consumption minimization, as such a gas is very expensive and hard to come by. We also focus on the properties of Si 0.26 Ge 0.74 and Si 0.21 Ge 0.79 Virtual Substrates (VS) grown at 850°C, 20 Torr and a forward Ge ramping-up on Si(001) substrates. After some chemical polishing (to remove the surface cross-hatch), those VS are used as templates for the 500°C, 100 Torr growth of SiGe/c-Ge/SiGe 2D Hole Gas Gas (2DHG) stacks. Those c-Ge layers are, in X-Ray Diffraction, fully compressively strained on the relaxed SiGe VS underneath and of high crystalline quality. Some slight undulations are evidenced at c-Ge / SiGe cap interfaces, hinting at elastic strain relaxation, however. Magnetotransport measurements in Hall-bar devices were performed at 4.2 K to assess the electrical properties of the 2DHG in those SiGe/c-Ge heterostructures. At low magnetic field, a hole mobility of 1.2 x 10 5 cm 2 V -1 s -1 was obtained for a hole density of n 2DHG = 3.7x10 11 cm -2 in a 16 nm thick c-Ge/55 nm thick Si 0.21 Ge 0.79 cap sample.