In this work, nitric acid oxidation was studied to fabricate the tunneling oxide of nanocrystal memory devices. SiO2 about 4 nm thick was formed through oxidizing the sputtered Si film by immersing in nitric acid solution (HNO3: H2 O=1:10) for 60 s. After oxide formation, a rapid thermal annealing process set at 700°C for 30 s was used to improve oxide quality. In addition, the formed SiO2 film was analyzed by X-ray photoelectron, capacitance-voltage, and current density-voltage measurements to study the process of the nitric acid oxidation. After the investigation of the nitric acid oxidized SiO2, a 6 nm thick cobalt silicide thin film was deposited and aggregated on the formed SiO2 layer as the charge-trapping layer. The cobalt silicide nanocrystal memory device showed an obvious memory effect and good reliability, which confirms that the nitric acid oxidation method has potential for memory application.