SEMICONDUCTOR DEVICE AND CONTROL METHOD THEREOF

摘要

A semiconductor device has a plurality of memory cells storing two bits of data in a cell, and a first reference cell (RCl) and a second reference cell (RC2) being shared by the plurality of memory cells. When programming the memory cell, programming a program subjected cell and refreshing a refresh subjected cell are both verified with a threshold value of the second reference cell corresponding to a programmed state of the memory cell. The second reference cell is programmed with a first threshold value (PRGV) to verify when programming, and is refreshed with a second threshold value (REFV) lower than the first threshold value to verify when refreshing.