In this research, the CBRAM-based synaptic devices for memristive synaptic array are designed. Pt-Al2o3-V3D3-Cu stack(~11nm) is used. pV3D3 has strength for its low k, high band gap, low temperature process, and BEOL compatible process. Retention characteristics of CBRAM-based synaptic devices are shared in the presentation. CBRAM-based synaptic devices has emphasis on fine tuning(maximum conductance ~4500uS) and reliable retention(4bit, >1.1x10^4 s) However, its poor switching endurance is still a remaining problem.