In this paper, we study the effect of highly doped Si as the bottom electrode on unipolar RRAM with Ni-electrode/ structure. With heavily doped -Si as the bottom electrode, RRAM devices illustrate the coexistence of the bipolar and the unipolar resistive switching. Meanwhile, by substituting heavily doped -Si, the switching behavior changes to that of the self-rectifying unipolar device. The asymmetry and rectifying reproducible behavior in a device resulted from the Schottky barrier of defect states in the junction and Si substrate, but this behavior is not seen for the -Si bottom electrode case. With rectifying characteristics and high forward current density observed in the device, the sneak current path in the conventional crossbar architecture was significantly suppressed. We believe that the proposed structure is a promising candidate for future crossbar-type RRAM applications.