the first sub sector thus the first sub sector may be erased as described above a nonvolatile memory device according to an embodiment of the inventive concept may perform an erase operation by a sector unit or by a sub sector unit using a sector selecting circuit ssc whether an erase operation is performed by a sector unit or by a sub sector unit may be determined at a circuit design step by a designer fig1 is a diagram schematically illustrating a memory cell array according to still another embodiment of the inventive concept a memory cell array 110 _ 2 in fig1 may be similar to that 110 _ 1 in fig1 thus similar elements may be marked by similar reference numerals for ease of description elements constituting a sector may be illustrated in fig1 referring to fig1 a sector selecting circuit ssc may be placed between two sectors one sector may include two sub sectors connected to different word lines and control gate lines each sub sector may be connected to the same word line and control gate line each sub sector may include two memory cells returning to fig1 each sector of a memory cell array 110 _ 1 may include eight memory cells further returning to fig1 each sub sector may include four memory cells on the other hand as illustrated in fig1 a sector selecting circuit ssc may be placed between two bit line pairs each sector may include four memory cells and each sub sector may include two memory.