Metal silicon‐nitriden‐p+silicon diodes have been fabricated withI‐Vcharacteristics similar to those of a four‐layer diode. Switching between the two impedance states, whose impedance levels differ by a factor of the order of 106, can be accomplished in less than 5 nsec. The impedance of the device is controlled by the presence or absence of the inversion layer of the MIS structure. Both impedance states require a nonzero conductance of the insulator.