A method for forming a magnetic memory device is disclosed. At least one magnetic tunneling junction (MTJ) stack is formed on the substrate. The MTJ stack comprises a reference layer, a tunnel barrier layer and a free layer. A top electrode layer is formed on the MTJ stack. A patterned sacrificial layer is formed on the top electrode layer. The MTJ stack is then subjected to a MTJ patterning process in a high-density plasma chemical vapor deposition (HDPCVD) chamber, thereby sputtering off the MTJ stack not covered by the patterned sacrificial layer. During the MTJ patterning process, sidewalls of layers or sub-layers of the MTJ stack are simultaneously passivated in the HDPCVD chamber by depositing a sidewall protection layer.