ε-Ga2O3, a metastable phase of Ga2O3, has excellent compatibility with substrates having a hexagonal structureor a quasi-hexagonal structure, so that a film having a relatively lower surface roughness and defect density than β-Ga2O3can be obtained easily. Accordingly, we attempted to fabricate a high-quality β-Ga2O3 film with a low surface rough nessand defect density using the property of phase transition to β-Ga2O3 when ε-Ga2O3 is annealed at a high temperature. Forthis, the growth of high-quality ε-Ga2O3 films must be preceded. In this study, the optimal flow rate was investigated byanalyzing the structural and morphological characteristics of the ε-Ga2O3 film according to the supplied precursor ratio. Inaddition, the annealing condition and the effect of β-Ga2O3 mixed in the ε-Ga2O3 film on the crystallinity of β-Ga2O3 afterphase transition were also investigated.