Y‐Ba‐Cu‐O (YBCO) films were grown on (100)MgO and (100)Si substrates by the high‐pressure dc diode sputtering process. The target was a Y1Ba2Cu3Oxcompound, made by a solid‐state reaction. The sputtering gas was Ar‐50% O2and the total pressure was 1.5 Torr. As‐deposited superconducting YBCO films can be prepared at low substrate temperatures (420 °C) with a high discharge current. The phases of the as‐deposited films strongly relate to the discharge current and substrate temperature. The high concentration of active species (excited atoms and ions) in the plasma during deposition is the main factor that permits superconducting YBCO films to be formed at such low substrate temperatures.