資料來源 : Free On-Line Dictionary of Computing

Ferroelectric Random Access Memory
     
         (FRAM) A type of {non-volatile} read/write {random
        access} {semiconductor} memory.  FRAM combines the advantages
        of {SRAM} - writing is roughly as fast as reading, and {EPROM}
        - non-volatility and in-circuit programmability.  Current (Feb
        1997) disadvantages are high cost and low density, but that
        may change in the future.  Density is currently at most 32KB
        on a chip, compared with 512KB for SRAM, 1MB for EPROM and 8MB
        for DRAM.
     
        A ferroelectric memory cell consists of a ferroelectric
        {capacitor} and a {MOS} {transistor}.  Its construction is
        similar to the storage cell of a {DRAM}.  The difference is in
        the dielectric properties of the material between the
        capacitor's electrodes.  This material has a high dielectric
        constant and can be polarized by an electric field.  The
        polarisation remains until it gets reversed by an opposite
        electrical field.  This makes the memory non-volatile.  Note
        that ferroelectric material, despite its name, does not
        necessarily contain iron.  The most well-known ferroelectric
        substance is BaTiO3, which does not contain iron.
     
        Data is read by applying an electric field to the capacitor.
        If this switches the cell into the opposite state (flipping
        over the electrical dipoles in the ferroelectric material)
        then more charge is moved than if the cell was not flipped.
        This can be detected and amplified by sense amplifiers.
        Reading destroys the contents of a cell which must therefore
        be written back after a read.  This is similar to the
        {precharge} operation in DRAM, though it only needs to be done
        after a read rather than periodically as with DRAM {refresh}.
        In fact it is most like the operation of {ferrite core
        memory}.
     
        FRAM has similar applications to EEPROM, but can be written
        much faster.  The simplicity of the memory cell promises high
        density devices which can compete with DRAM.
     
        {RAMTRON} is the company behind FRAM.
     
        (1997-02-17)