| 摘要 |
<p>PROBLEM TO BE SOLVED: To restrict a spread of a threshold value distribution by writing to a memory cell sequentially from a write state of a large difference of a quantity of electric charges in a floating gate to an erase state. SOLUTION: Memory cells M are arranged in rows and columns to form arrays, and a plurality of row lines (WL0-WLn) for connecting control gates of memory cells M constituting the rows and seven column lines (BL0-BL6) for connecting in common drains and sources of memory cells M constituting the columns are set in the memory. In programming to the memory, a quantity of electric charges of each floating gate is changed thereby providing one memory cell M with a plurality of memory states, so that four values of memory states '11', '10', '01' and '00' can be stored. Writing to the memory is carried out sequentially from a write state of a large difference of the quantity of electric charges in the floating gate to an erase state (data '00').</p> |
