Patent ID: 7872933

Claim:
A method of driving a memory including memory cells, bit lines, and word lines, each memory cell having a source, a drain, and a floating body in an electrically floating state, the memory cells storing logical data according to the number of carriers in the floating bodies, the bit lines being connected to the drains, the word lines intersecting the bit lines, the method comprising: performing a refresh operation for recovering deterioration of first logical data of the memory cells and deterioration of second logical data of the memory cells, the number of the carriers accumulated in the floating body of the memory cell storing the second logical data is smaller than that of the memory cell storing the first logical data, wherein in the refresh operation, the number of the carriers injected into the floating body is larger than the number of the carriers discharged from the floating body when a potential at the floating body is larger than a critical value, and the number of the carriers injected into the floating body is smaller than the number of the carriers discharged from the floating body when the potential at the floating body is smaller than the critical value.