Non-volatile memory devices and methods of programming a non-volatile memory device in which electrons are moved between charge trap layers through a pad oxide layer are provided. The non-volatile memory devices include a charge trap layer on a semiconductor substrate and storing electrons, a pad oxide layer on the first charge trap layer, and a second trap layer on the pad oxide layer and storing electrons. In a programming mode in which data is written, the stored electrons are moved between a first position of the first charge trap layer and a first position of the second charge trap layer through the pad oxide layer or between a second position of the first charge trap layer and a second position of the second charge trap layer through the pad oxide layer.