Cross-point memory framework provides high capacity, low power consumption, and low cost in nonvolatile-memory (NVM) technology [1,2]. Resistive cross-point memory structure is one of the potential candidates with scaling down beyond the flash memory . In order to increase density for cross-point architecture, the vertical diode is integrated for the controller (Fig. 1) without planar MOSFET or BJT. The metal oxide diode has been reported on the switching devices with high leakage current . The p/n diode has higher ON-current and uni-polar operation for PCM (Phase Change Memory) [5,6], which is compatible with IC process. The characteristic of bipolar programming in RRAM makes the requirement of bi-directional turn-ON behavior for the switching driving device . In this work, the poly-Si n/p/n diode with ambipolar operation for RRAM applications and the stress reliability for programming will be demonstrated.