Semiconductor memory

Semiconductor memory is an electronic data storage device, often used as computer memory, implemented on a semiconductor-based integrated circuit. Examples of semiconductor memory include non-volatile memory such as Read-only memory (ROM), magnetoresistive random access memory (MRAM), and flash memory. It also includes volatile memory such as static random access memory (SRAM), which relies on several transistors forming a digital flip-flop to store one bit, and dynamic random access memory (DRAM), which uses one capacitor and one transistor to store each bits. Shift registers, processor registers, data buffers and other small digital registers that have no memory address decoding mechanism are not considered as memory.

Data is accessed by means of a binary memory address to the memory. If the memory address consists of M bits, the address area consists of two raised by M addresses per chip. Semiconductor memory are manufactured with a certain word length (number of 1-bit cells sharing the same memory address) that power of two, typically M=1, 2, 4 or 8 bit per chip. Consequently, the amount of data stored in each chip is $MN^{2}$ bits. Possible figures are 1, 2, 4, 8, 16, 32, 64, 128, 256 and 512 bit, kbit, Mbit, Gbit and Tbit, here defined by binary prefixes. By combining several integrated circuits, memory can be arranged for a larger word length and/or address space than what is offered by each chip, often but not necesserily a power of two.