Memory Design

Semiconductor memories are digital electronic semiconductor devices used for the digital information storage of program code and data. As the demand keeps growing, new memory technologies are continuously introduced and the existing technologies are further developed. A variety of semiconductor memories are in development with different concepts of memory cells for various applications. There are two main categories of memories, i.e., volatile memory (VM) and nonvolatile memory (NVM). VM needs to be provided power constantly to retain data, such as static random access memory (SRAM), which uses several transistors per memory cell, and dynamic random access memory (DRAM), which uses a single transistor and a capacitor per cell. In contrast, NVM retrieves stored information even after the power goes down. Examples of NVM include read-only memory (ROM), flash memory with floating gate MOS transistor per cell, and several emerging memories, such as ferroelectric RAM (FeRAM), spin transfer torque magnetoresistive RAM (STT-MRAM), resistive RAM (RRAM), and phase change RAM (PCM). Semiconductor memories are available in various forms: IP for system-on-chip, discrete components for assembly, memory cards, and solid-state hard drives. Usually a semiconductor memory works with memory controller, which bridges memories and corresponding host computers, and also manages the operation of memories accordingly.