An information memory device capable of reading and writing of information by mechanical operation of a floating gate layer, in which a gate insulation film has a cavity (6), and a floating gate layer (5) having two stable deflection states in the cavity (6), the state stabilized by deflecting toward the channel side of transistor, and the state stabilized by deflecting toward the gate (7) side, writing and reading of information can be made by changing the stable deflection state of the floating gate layer (5) by Coulomb interactive force between the electrons (or positive holes 8) accumulated in the floating gate layer (5) and external electric field, and by reading the channel current change based on the state of the floating gate layer (5).