PURPOSE: To improve the charge injecting efficiency so as to increase the data writing speed of a nonvolatile storage device by injecting the charges from a source area side.

CONSTITUTION: Such a low voltage that at which the channel 14 of a nonvolatile storage element in which information is written can be barely turned on is applied across a select gate line constituting the select gates 161-163 of the storage element and a high voltage is applied across a word line constituting a gate. At the writing time of the information, a surface potential gradient is generated between the select gates 161-163 and charge storing layers 181-183 and electric fields are concentrated below tunnel insulating films 17 between the gates 161-163 and layers 181-183 in a selected nonvolatile storage element. As a result, high-energy charges are generated and the charges are injected into the layers 181-183 from their source area 13a sides by FN-tunneling the insulating films 17.