A bipolar resistive switching memory device with a low power operation (200 mu Ax1.3 V) in a W/Ge0.4Se0.6/Cu/Al structure is investigated. A high quality Ge0.4Se0.6 solid electrolyte is confirmed by X-ray photoelectron spectroscopy. The resistive memory device with a small via size of 0.2 mu m has a large threshold voltage of >0.4 V, high resistance ratio (R-high/R-low) of >10(2), and good uniformity. The switching mechanisms are due to the Cu metallic filament formation and dissolution from the Ge0.4Se0.6 solid electrolyte under positive and negative biases, respectively, which have been confirmed by high resolution transmission electron microscopy image and energy-dispersive X-ray spectroscopy analysis. The strong Cu filament formation can also be investigated by monitoring the erase voltage and erase current. Good endurance of >10(5) cycles is obtained. Excellent data retention characteristics at 85 degrees C are observed after 24 h of retention time, owing to the strong Cu metallic filament formation in the Ge0.4Se0.6 solid electrolyte.