A method of manufacturing a non-volatile memory is provided. A substrate including a first region and a second region is provided. A first patterning process is performed to the first region, so as to form a plurality of gate stack structures in the first region. Afterwards, a first sidewall oxide layer is formed to cover sidewalls and an upper surface of each gate stack structure, and a protection layer is then formed on the first sidewall oxide layer. Next, an ion implantation process is performed to the second region, and a second patterning process is performed to the second region so as to form a plurality of gate structures. Then, a second sidewall oxide layer covering sidewalls of each gate structure is formed.