Spin-transfer-torque (STT) MRAM has emerged as one of the most promising new memory technologies for future SRAM and embedded Flash replacement due to its non-volatility,fast read and write time,smallsize, intrinsic-infinite endurance and compatibility with CMOS technology. There are still many remaining challenges to overcome for STT-MRAM to be commercialized as disruptive memory technology, especially at sub-10nm dimension:lowering the critical switching current while maintaining adequate thermal energy barrier, increasing tunneling magneto-resistance(TMR) and controlling the resistance distribution, developing re-disposition-free and edge-damage-free patterning process and robust MgO barrier for enough separation between switching and the breakdown voltage.