A semiconductor memory device may include a semiconductor substrate, a control gate electrode recessed in the semiconductor substrate, a storage node layer between the control gate electrode and the semiconductor substrate, a tunneling insulating layer between the storage node layer and the semiconductor substrate, a blocking insulating layer between the storage node layer and the control gate electrode, and first and second channel regions surrounding the control gate electrode and separated by a pair of opposing separating insulating layers. A method of operating the semiconductor memory device may include programming data in the storage node layer by charge tunneling through the blocking insulating layer, thus achieving relatively high reliability and efficiency.