In this rising field of portable electronics, all solid state thin film supercapacitors (ASSTFSs) have received tremendous courtesies due to their flexibility and high safety, which are considered as competitive candidates for energy power sources in flexible electronics. In present investigation, we demonstrate the first successful application of pseudocapacitive RuO2 in ASSTFS, exhibiting high capacitance, remarkable high-rate capability and long-term cycling stability. Nanocrystalline RuO2 thin films are developed on mesh like stainless steel substrate by facile chemical bath deposition (CBD) method at three different deposition temperatures. ASSTFSs were fabricated by simple process using two slightly separated RuO2 thin films well solidified in the H2SO4–polyvinyl alcohol gel electrolyte. Electrochemical studies of ASSTFS device was characterized by cyclic voltammetry, charge–discharge and impedance techniques. The highest specific capacitance of 234, 203 and 167Fg−1 for three RuO2 nanostructures was obtained. Further the device shows good stability after 1000 cycles. The non-ideal behavior of the supercapacitor was analyzed by impedance analysis. Additionally, the all-solid-state nature combined with superior electrochemical performance makes RuO2-based device an excellent candidate for power sources in portable electronics.