We investigated the dependencies of the saturation field, H_s, for synthetic ferrimagnetic (SyF) structures with various stacking structures on annealing temperature and Ru middle layer thickness. The buffer layer was optimized using Co₇₅Fe₂₅/Ru/Co₇₅Fe₂₅-SyF. The SyF on the Ta/Ru buffer layer demonstrated high annealing stability and large H_s. Moreover, we investigated the dependence on annealing temperature of H_s for Ta(5 nm)/Ru(5 nm)/ ferromagnetic-layer/Ru(0.8 nm)/Co₄₀Fe₄₀B₂₀(2 nm) SyFs with various ferromagnetic layers. The SyFs using Co₇₅ Fe₂₅ and Ni₈₀Fe₂₀ ferromagnetic layers exhibited high annealing stability and large H_s. The dependence on Ru middle layer thickness of H_s for the SyFs consisting of Ta(5 nm)/Ru(5 nm)/Co₇₅ Fe₂₅(2 nm)/Ru(0.2-1.2 nm)/Co₄₀Fe₄₀B₂₀(2 nm)/ MgO(2.5 nm)/Ta(10 nm) was investigated. As a result, we demonstrated the possibility of fabricating CoFeB/MgO/ CoFeB MTJs with SyF having both high annealing stability and strong interlayer exchange coupling.