| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a means for preventing erroneous reading in a reading operation by preventing rewriting to a storage element to which storage information "0" is once written. <P>SOLUTION: In the nonvolatile semiconductor storage device equipped with two storage elements obtained by laminating a first silicon oxide film, an electric charge accumulating nitride film and a second silicon oxide film, at both sides of a gate electrode, a writing voltage in a case when the electric charge is injected to the electric charge accumulating nitride film by dividing it into a plurality of the number of times, is set so as to be increased stepwise between an initial writing voltage and a set writing voltage, and also a target current for confirming the holding state of the electric charge by using a cell current is set so as to be increased stepwise between an initial target current to a set target current with an inclination larger than that increases a cell current by the change of the electric charge holding state, and when the electric charge is injected to the storage element, the electric charge is injected to the storage element by the writing voltage when the cell current exceeds the target current, and the electric charge is not injected to the storage element when the cell current is equal to the target current or smaller. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
