Resistive switching behaviors are studied for the rapid thermal annealing (RTA) Ga 2O 3 thin film embedding a Cr metal layer. By modifying the thickness, area, and RTA temperature of the device, the thermal-induced resistive switching is similar to those induced by the electrical forming process. The conducting filaments composed of oxygen vacancies are created by the Cr diffusion and oxidization during RTA. The related carrier conduction mechanism obeys space charge limited conduction theory accompanied by the formation/rupture of the conducting filaments at the interface between Ti and Cr:Ga 2O 3 film. This study demonstrates a convenient process to fabricate forming-free resistive switching memory devices.