Amorphous semiiconductor layer memory device

A memory device includes: an amorphous semiconductor layer of a first conduction type; a solid electrolyte layer containing movable ions and provided in contact with a part of one of faces of the amorphous semiconductor layer; a first electrode electrically connected to the amorphous semiconductor layer via the solid electrolyte layer; a second electrode electrically connected to one of the faces of the amorphous semiconductor layer; and a third electrode provided over the other face of the amorphous semiconductor layer with an insulating layer therebetween. At the time of application of voltage to the third electrode, at least a part of the amorphous semiconductor layer reversibly changes to a second conduction type.