MEMORY ELEMENT, MONVOLATILE MEMORY, NONVOLATILE STORAGE DEVICE, AND METHOD FOR STORING INFORMATION BY USE OF THE STORAGE DEVICE

摘要

A DRAM having a special mode, a nonvolatile memory cell having the DRAM therein, and a nonvolatile semiconductor storage device having a structure like a DRAM and capable of writing and erasing data with a high precision. There are provided a sub-bit line BLs1 connected to the main bit line BL1 through a selecting transistor Tr1, and nonvolatile cells (memory transistors) M1 to Mn of drain electrodes are connected to the sub-bit line BLs1. Writing and erasing are executed by applying an a.c. voltage from an a.c. pulse generator to the control gate of each of the nonvolatile memory cells M1 to Mn. A DRAM cell is made up of a capacitor element formed by the parasitic capacitance of a sub-bit line BLs1 and the drain electrodes of the nonvolatile memories M1 to Mn connected to the sub-bit line BLs1, and the selecting transistor Tr1. An arbitrary nonvolatile memory cell Mk is connected to the memory node N of the DRAM cell. Thus, the nonvolatile memory cell having the DRAM function and the nonvolatile storage device are constituted. The DRAM cell unit functions independently, and the DRAM cell unit accumulates data temporarily. The data are transferred to the nonvolatile memory cell Mk, hence improving the writing speed, decreasing the size of the apparatus, and executing highly reliable writing and erasing.