The conductive-bridge random access memory (CBRAM) has become one of the most suitable candidates for non-volatile memory in next-generation information and communication technology. The resistive switching (RS) mechanism of CBRAM depends on the formation/ annihilation of the conductive filament (CF) between the active metal electrode and the inert electrode. However, excessive ion injection from the active electrode into the solid electrolyte reduces the uniformity and reliability of the RS devices. To solve this problem, we investigated the RS characteristics of a CuSn alloy active electrode with different compositions of Cu-x-Sn1-x (0.13 < X < 0.55). The RS characteristics were further improved by inserting a dysprosium (Dy) or lutetium (Lu) buffer layer at the interface of Cu-x-Sn1-x/Al2O3. Electrical analysis of the optimal Cu-0.4-Sn-0.(73)/Lu-based CBRAM exhibited stable RS behavior with low operation voltage (SET: 0.7 V and RESET: -0.3 V), a high on state/off state resistive ratio (10(6)), AC cyclic endurance (>10(4)), and stable retention (85 degrees C/10 years). To achieve these performance parameters, CFs were locally formed inside the electrolyte using a modified CuSn active electrode, and the amount of Cu-ion injection was reduced by inserting the Dy or Lu buffer layer between the CuSn active electrode and the electrolyte. In particular, conductive-atomic force microscopy results at the Dy or Lu/Al2O3 interface directly showed and defined the diameter of the CF.