Thin film processes for the high Tc superconductors of perovskite‐type oxides are classified into three: (1) deposition at a low substrate temperature followed by a post‐annealing at around 900°C; (2) deposition at a crystallization temperature 600–800°C, followed by the post‐annealing; (3) deposition at the crystallization temperature under oxidizing atmosphere. The process (3) possibly lowers the synthesis temperature. It was confirmed that the superconducting thin films of Er‐Ba‐Cu‐O were successfully grown at 650°C by the sputtering deposition owing to the process (3). Their onset temperature was 92K with zero‐resistivity at 86K.