| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase storage capacity, by making a first floating gate and a control gate which are formed on a source and a drain a readout part, and making a second floating gate and a program gate which are formed on a high impurity concentration layer an erasing part. SOLUTION: At the time of readout mode, the amount of a current flowing between a drain 3 and a source 2 is detected by applying a voltage to a control gate 5. The threshold voltage of a first floating gate 4A is detected by charges charged on second floating gates 4B1 , 4B2 , and stored information is read out. At the time of program mode, a voltage is applied to a program gate 62 , and the high impurity concentration layer 22 is grounded. Then FN tunneling is generated between a tunnel oxide film formation part 4B20 and the high impurity concentration layer 22, and implantation is performed to the second floating gate 4B2 . At this time, implantation is not performed to the second floating gate 4B1 by an insulating layer 10.</p> |
