Memories based on semiconductors are called semiconductor memories. In terms of basic principle, such a memory consists of an electronic toggle circuit that has one or two stable states. Alternatively, there are electronic memory cells with semiconductors that store the logic states in capacitors.
A flip-flop is a bistable multivibrator or flip-flop, it consists of two transistors that control each other. If one transistor is conducting current, which is to be interpreted as a logic "1", then the other is in a current blocking function, this is to represent logic "0". Such a circuit has two states, zero and one, and can store 1 bit. Another semiconductor technology used in memory cells and bit cells for storing logic states uses FETs and capacitors in which the logic state is stored.
Thanks to semiconductor technology and the ever more compact design of integrated circuits, it is possible to integrate memory devices with many megabytes on one chip.
Depending on the concept and structure of the semiconductor memory, these can be static memories or read-only memories, such as read-only memories( ROM), and also dynamic memories or RAMs with changeable memory content, such as random access memories( RAM) or flash memories. Of these basic types, there are various variants such as Static RAM( SRAM), Dynamic RAM ( DRAM), Ferro RAM( FRAM) and Magneto-Resistive RAM( MRAM), as well as NAND Flash and NOR Flash. The mentioned semiconductor memories differ in the write speed and the read speed, the erase process, the storage time, the cell density and in some other characteristic values.
The first semiconductor memories were introduced in 1968 in MOS technology and had an integration density of 200 flip-flops on a chip.