Non-volatile memory devices are disclosed. In a first example non-volatile memory device, programming and erasing of the memory device is performed through the same insulating barrier without the use of a complex symmetrical structure. In the example device, programming is accomplished by tunneling negative charge carriers from a charge supply region to a charge storage region. Further in the example device, erasing is accomplished by tunneling positive carriers from the charge supply region to the charge storage region. In a second example non-volatile memory device, a charge storage region with spatially distributed charge storage region is included. Such a charge storage region may be implemented in the first example memory device or may be implemented in other memory devices. In the second example device, programming is accomplished by tunneling negative charge carriers from a charge supply region to the charge storage region. In the second example device, the tunneled negative charge carriers are stored in the discrete storage sites.