15. A memory device, comprising: a substrate; and a plurality of word line groups disposed on the substrate and each comprising: at least one word line; and at least one dummy word line adjacent to the at least one word line, wherein the at least one dummy word line and the at least one word line have the same potential, wherein two dummy word lines are respectively disposed on two sides of each of the word lines.
15. A memory device, comprising: a substrate; and a plurality of word line groups disposed on the substrate and each comprising: at least one word line; and at least one dummy word line adjacent to the at least one word line, wherein the at least one dummy word line and the at least one word line have the same potential, wherein two dummy word lines are respectively disposed on two sides of each of the word lines. 17. The memory device according to claim 15 , wherein a portion of the word lines is contacted with a portion of the dummy word lines of the word line group.