A first semiconductor layer 1 is formed on a substrate, a first impurity layer 3 and a second impurity layer 4 extending in a vertical direction are sequentially disposed on part of the first semiconductor layer 1, their sidewalls and the semiconductor layer 1 are covered by a second gate insulating layer 2, a gate conductor layer 22 and a second insulating layer are disposed in a groove formed there, and a second semiconductor layer 7, n+ layers 6a and 6c positioned at respective ends of the layer 7 and connected to a source line SL and a bit line BL, respectively, a second gate insulating layer 8 formed to cover the second semiconductor layer 7, and a second gate conductor layer 9 connected to a word line WL are disposed on the second impurity layer. Voltage applied to the source line SL, a plate line PL connected to the first gate conductor layer 22, the word line WL, and the bit line BL is controlled to perform data holding operation of holding, near the gate insulating layer, holes generated by an impact ionization phenomenon in a channel region of the second semiconductor layer or by gate-induced drain leakage current, and data erase operation of removing the holes in the channel region 12.