Current scaling challenges for memory technology have led to fast-paced development of alternative memory technologies. STT-RAM is the leading potential candidate to replace static RAM, dynamic RAM and embedded memory due to its non-volatility, high speed, and unlimited endurance. The performance of STT-MRAM such as memory signal strength (TMR) and data retention (coercivity) is primarily determined by the MTJ film. The deposition of MTJ film requires an underlayer with Angstrom-scale smoothness to achieve good device performance. The Applied Materials Reflexion® LK Prime™ CMP system was used to develop a CMP process to achieve such Angstrom-scale smoothness on the patterned bottom plug-oxide boundary. This degree of smoothness on the bottom plug helped to significantly improve the device performance.