A method for forming a memory device is disclosed, including providing a substrate, forming an isolation structure and plural active regions in the substrate, forming a plurality of island features on the substrate respectively covering two of the terminal portions of the active regions, using the island features as an etching mask to etch the substrate to perform a first etching process to define a first recessed region and plural island structures on the substrate. The island structures respectively comprise the two terminal portions of the active regions and the first recessed region comprises the central portions of the active regions.