Patent ID: 8223548

Claim:
A memory device, comprising: a first semiconductor member having a generally columnar shape having an operative length and a first surface along the operative length, said generally columnar shape defining a cross section that would appear when cut in a direction perpendicular to the operative length; a memory means provided on the first surface of the first semiconductor member, the memory means at least partially surrounding the first semiconductor member at a location at which said cross section is defined; and a gate provided on the memory means, and wherein: said first semiconductor member includes one of silicon, germanium, and compound semiconductor, said memory means includes one of an insulation film including a layer of charge trapping atoms, a multilayered insulation films, and a ferroelectric material, an equivalent sectional radius of the cross section of the first semiconductor member is set to be equal to or smaller than an equivalent silicon oxide film thickness of the memory means, said equivalent sectional radius is defined as a radius of curvature of a circle having the same cross-sectional area as the area of the cross section of said first semiconductor member, and said equivalent silicon oxide film thickness of the memory means is defined as a thickness of the memory means in a direction normal to the first surface of the first semiconductor member on which the memory means is provided, multiplied by the dielectric constant of silicon oxide and divided by the dielectric constant of the memory means, and when the memory means essentially consists of a plurality of layers, said equivalent oxide film thickness of the memory means is a sum of all of the equivalent silicon oxide film thicknesses of the respective layers constituting the memory means.