Nonvolatile random access memory

A nonvolatile random access memory having a nonvolatile memory cell storing one-bit data, wherein

• the memory cell comprises:
• a first Metal-Insulator-Semiconductor (MIS) transistor formed of a first semiconductor layer of a first conductivity type which is in an electrically floating state, a first drain region and a first source region made of an impurity diffusion region of a second conductivity type that is opposite to the first conductivity type formed on a surface of the first semiconductor layer, and a first gate electrode formed through a first gate insulating film over the surface of the first semiconductor layer between the first drain region and the first source region;
• and
• a second MIS transistor formed of a second semiconductor layer of the first conductivity type that is isolated from the first semiconductor layer, a second drain region and second source region made of an impurity diffusion region of the second conductivity type formed on a surface of the second semiconductor layer, a second gate electrode formed through a second gate insulating film over the surface of the second semiconductor layer between the second drain region and the second source region,
• the first gate electrode and the second gate electrode are electrically connected to each other so as to form a floating gate in an electrically floating state,
• one-bit date is stored in a volatile manner by controlling a threshold voltage of the first MIS transistor in accordance with an amount of charge in the first semiconductor layer in a first storage mode, and
• one-bit data is stored in a nonvolatile manner by controlling a threshold voltage of the second MIS transistor in accordance with an amount of charge in the floating gate in a second storage mode.