Interfacial effects on magnetic properties are investigated for the as-deposited and annealed Co64Fe16B20 films with different under-layers (Cu, Ru, or Pd). The intrinsic Gilbert damping factor is inferred to be slightly lower than the obtained value of 0.007. We found that both the in-plane coercivity Hc and ferromagnetic resonance linewidth ΔHpp rely on the interfacial morphology. The Cu under-layer provides a rough surface, which offers an extra contribution to the ΔHpp. The surface roughness was greatly enhanced by post-annealing for Cu, while little affected for Ru and Pd. Resultingly, the ΔHpp and Hc of Cu/CoFeB increase significantly after annealing. However, for the annealed Ru/CoFeB sample, the ΔHpp even decreases implying Ru is a proper under-layer material for CoFeB-based spintronic devices.