Advanced Capacitor and Supercapacitor Structures Based on Functional Thin Films

Thin-film capacitors and supercapacitors are gaining increasing attention due to the rapid development of modern electronics, flexible devices, microsystems and wearable technologies. Their small size, low weight and compatibility with integrated electronic systems make them promising components for next-generation applications and energy-storage systems. In recent years, significant progress has been achieved in the development of thin-film structures with improved capacitance, higher energy density, lower leakage current and better thermal and electrical stability. Advances in thin-film engineering have also enabled the use of high-k dielectric materials, ultrathin insulating layers, oxide-based electrodes and advanced carbon materials to enhance device performance. This review presents recent progress in thin-film capacitor and supercapacitor technologies, focusing on device architectures, dielectric and electrode thin films and reliability-related challenges. Different configurations, including metal–insulator–metal (MIM), metal–oxide–semiconductor (MOS), interdigital, flexible and three-dimensional structures, are discussed. Special attention is given to oxide thin films, nanostructured electrodes, interface quality, defect-related phenomena and scaling effects influencing electrical performance. Current market trends and commercial perspectives are also discussed in the context of emerging electronic applications. Finally, key technological challenges and future development directions for thin-film capacitors and supercapacitors are highlighted.