US Patent 7839711 Semiconductor memory device and driving method thereof

A memory including; cells, wherein a refresh operation includes a first refresh and a second refresh, in the first refresh, a first potential higher than a gate potential in a retention is applied to the gate in a state having a source potential applied to the drain, and thereafter the gate potential in the retention is applied to the gate, thereby a first current passes to the cell, and in the second refresh, a second potential higher than a gate potential in the retention is applied to the gate, and a third potential higher than the gate potential in the retention is applied to the drain, thereby a second current passes to the cell, and a state of the cell is shifted to an equilibrium state in which amounts of the first and the second currents flowing during one cycle becomes substantially equal.