An array structure of single-level poly NMOS EEPROM memory cells and method of operating the array is discussed implemented in a higher density embedded EEPROM layout that eliminates the use of high voltage transistors from the array core region. If they are utilized, the high voltage transistors are moved to row and column drivers in the periphery region to increase array density with little or no added process complexity to allow economic implementation of larger embedded SLP EEPROM arrays. During program or erase operations of the array, the method provides a programming voltage for the selected memory cells of the array, and a half-write (e.g., mid-level) voltage to the remaining unselected memory cells to avoid disturbing the unselected memory cells of the array.