A non-volatile semiconductor memory device includes a memory array having a cell string. The cell string includes a plurality of normal memory cells, a ground selection transistor gated so as to provide a source voltage to the normal memory cells, at least two dummy cells connected between a normal memory cell on one side end of the cell string and the ground selection transistor, wherein the normal memory cells are configured to store data and the dummy cells are configured to not store data. The memory device also includes a word line selection block which controls normal word lines to gate the normal memory cells and dummy word lines to gate the dummy cells, wherein the dummy word lines are controlled as sequential voltage levels during a program operation to select the normal memory cell on the one side end.