ABSTRACT
Silicon based digital memories are an information storage device where such information is stored in unit memory cells. Currently, these unit memory cells are built with complementary metal-oxide-silicon (CMOS) technology wherein each memory cell consists of one to several CMOS transistors. The prominent volatile silicon based digital memories employed in systems today are static random access memory (SRAM) and dynamic random access memory (DRAM). Read-only memory (ROM) arrays are laid out in similar architecture as those of static random access memory (SRAM) or DRAM containing the functional blocks discussed earlier. NAND flash memories are dense and lowest cost/bit among all silicon based volatile and nonvolatile memories. The latest of such transistor technology had been the CMOS-field-effect transistor (FET) technology, which dominated the digital memory products since 1980s. Such memories could be either "volatile" where binary memory states are lost if power supply is withdrawn or "nonvolatile" where the memory states could be retained even when the power supply is removed.
