Amorphous SiO2 thin films were fabricated at different temperatures using sol-gel technique. The unipolar resistive switching behavior was observed in Cu/ SiO2/ ATO (SnO2: Sb) sandwiched structure when the SiO2 thin film annealed at 500°C. The average ratio of Roff /Ron is 102. We investigated the successful device using HRTEM and XPS. It shows that the Cu defuses into the SiO2 thin film and it forms CuSiO3 in the interface between SiO2 and ATO films according to the high resolution images.