Method of manufacturing memory device using self-aligned double patterning (SADP)

A method of manufacturing a memory device, comprising:

• providing a semiconductor substrate defined with an active area disposed over or in the semiconductor substrate;
• forming a first hard mask over the semiconductor substrate;
• forming a core over the first hard mask, wherein the core has a strip portion and a protruding portion protruding laterally from the strip portion;
• forming a spacer surrounding the core;
• removing the strip portion of the core;
• removing portions of the first hard mask exposed through the spacer and the protruding portion of the core to form a plurality of slots in the first hard mask;
• forming a second hard mask surrounding the first hard mask and disposed within the plurality of slots, wherein the second hard mask includes a plurality of strips extending parallel to each other;
• removing the first hard mask;
• and
• removing portions of the semiconductor substrate exposed through the second hard mask to form a plurality of trenches surrounding the active area.