The CEA is developing an original spin qubit platform based on "silicon-on-insulator" (SOI) technology and is now turning to new pathways in Si/SiGe (electrons) and Ge/SiGe (holes). This activity is carried out by a consortium bringing together three of major laboratories in Grenoble: CEA-IRIG, CEA-LETI and CNRS-Néel. On this SOI platform, Grenoble has, for example, demonstrated the electrical manipulation of a single electron spin, as well as the first hole spin qubit, and recently obtained record lifetimes and spin-photon coupling for hole spins. In this context, it is essential to support the development of these advanced quantum technologies with advanced theory and modeling. CEA-IRIG is actively developing TB_Sim code. TB_Sim is able of describing highly realistic qubit structures down to the atomic scale if needed, using atomistic strong bonding models and multi-band k.p models for the electronic structure of materials. Using TB_Sim, CEA has recently examined various aspects of spin qubit physics, in close collaboration with experimental groups in Grenoble and with CEA partners in Europe. The first objective of this research work is to strengthen our understanding of electron spin qubits based on Si/SiGe heterostructures through analytical modeling as well as advanced numerical simulation using TB_Sim. The second objective is to compare the performances of the Si/SiGe platform to other Ge/SiGe and Si MOS platforms to identify its strengths and weaknesses.