A SnO2-RuO2 composite thin film has very high potential for a hybrid of battery and supercapacitor since SnO2-RuO2 system might show battery and supercapacitor characteristics simultaneously. A SnO2-RuO2 composite thin film prepared by a magnetron direct current (dc) co-sputtering method in order to investigate a feasibility of monolithic thin film hybrid battery. The as-deposited SnO2-RuO2 composite thin film showed crystalline peaks in the X-ray diffraction (XRD) patterns. Rutherford backscattering spectrometry (RBS) and Auger electron spectrometry (AES) analysis were conducted to identify the composition of the as-deposited film. The SnO2-RuO2 composite thin film as an anode film for secondary battery demonstrated the first discharge capacity of 400 400muAh/cm(2) mum. The discharge curve of the SnRuO composite thin film did not exhibit the 0.8-1.0 plateau characteristic of SnO2. For SnRuO composite thin film electrode, a plateau at around 1.2 V was observed in the first cycle only. A degree of capacity fade of the SnO2-RuO2 composite thin film was almost same to that of the SnO2 thin film, while the capacity of the SnO2-RuO2 thin film was larger than that of the pure SnO2. In the mean time, the SnO2-RuO2 composite thin film as an electrode for supercapacitor exhibited a specific capacitance of 62.2 mF/cm(2) mum. These results suggested that the SnO2-RuO2 thin film could be used for thin film supercapacitor as well as thin film battery. Furthermore, this composite thin film holds promise for fabrication of monolithic thin film high power hybrid battery based on micro-processes. (C) 2004 Elsevier Ltd. All rights reserved.