A bipolar RRAM device based on Ni/HfO2/n+-Si structure with self-rectifying characteristics is demonstrated for high density cross-bar memory application. Experimental results indicate that Ni conductive filament generated at LRS plays an important role in resistive switching, resulting in the formation of a Schottky junction at the Ni-CF/n+-Si interface which determines the self-rectifying behavior at LRS. These results are very important from the point of view of understanding the self-rectifying switching mechanism and improving the resistive switching characteristics of self-rectifying RRAM devices.