(201)-oriented β-Ga2O3/GaN thin films were epitaxially grown by pulsed laser deposition. These films have the specific in-plane orientation, which was confirmed by φ scans of Ga2O3 (111) and (311) reflections. When oxygen flow rate was increased, the surface morphologies and roughness of β-Ga2O3 drastically changed. The β-Ga2O3/GaN structure showed a stable and sharp interface and uniform elemental distribution in depth. The dielectric constant and memory window of β-Ga2O3/GaN were about 13.9 and 0.50 V for oxygen flow rate of 5 SCCM (SCCM denotes cubic centimeter per minute at STP).