History of MOS Memory Evolution on DRAM and SRAM

The memory capacity of DRAM has dramatically increased for half a century since the launch of 1-kbit DRAM in 1970. Specifically the invention of one-transistor-type memory cell (1T-cell) accelerated the DRAM evolution in corporation with the inventions of three-dimensional (3D) memory cells, stacked capacitor cell, and trench capacitor cell. Innovative technologies of DRAM in the past are described in this article referring to the background of 3D memory cell inventions. This article also describes the evolution of SRAM which started by employing 6 transistor (6T) CMOS memory cell and continued to develop innovative technologies to support the scaling the memory cell.