| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase the degree of integration of a semiconductor device by providing two floating gates under control gates having minimum dimensions, causing each floating gate to be able to represent two states by whether charges are being stored or not, and decreasing area required per two states. SOLUTION: On a channel region on the surface of a P-type semiconductor substrate 7, a first insulating film 8, a first floating gate 3, a second insulating film 9, a control gate 5 are formed. There is a third insulating film 13 on the surfaces of a source 1 and a drain 2, and isolates the control gate 5 from the source 1 and the drain 2 electrically and a P<+> region 10 is formed at a site where a channel 1 under the second floating gate 4 touches the drain 2. First and second floating gates 3, 4 are insulated and isolated electrically by a fourth insulating film 13. As a result of this, write operation into a memory cell is performed by write operation in the first floating gate 3 and that in the second floating gate 4 after that, and write operation of four states can be performed.</p> |
