We have improved surface resistance (RS) properties of ErBa 2Cu3O7-δ(ErBCO) films by using BaTiO 3(BTO) doping (BTO+ErBCO). The as-grown BTO+ErBCO films did not have enough carriers. We solve this problem by using O3+O2 as background gas during the growth of BTO+ErBCO films. Then, O3+O 2 gas is useful to grow BTO+ErBCO films with superior superconducting properties. The RS of a 2wt%BTO+ErBCO film is the lowest in BTO+ErBCO films grown in this study. This value is equal to that of a 1.5wt%BZO+ErBCO film. The microstructures of the 2wt%BTO+ErBCO film are observed by transmission electron microscopy (TEM). In the image, the BTO+ErBCO films did not have nanorods as the observed in BZO+ErBCO films against our expectation. However, the precipitates what BZO+ErBCO films do not have, are observed.