Abstract A metal insulated semiconductor (MIS) field effect transistor is operated in a gate-to-source mode. The voltage threshold of conduction of the transistor is variable and is switched between two different stable threshold conditions in response to application of corresponding, different predetermined values of polarizing voltages applied between the gate and source terminals. Determination of the threshold condition to which the transistor is switched is effected by applying a read voltage to the gate of the transistor intermediate the voltage threshold levels and sensing the current flow between the source and drain. Since the sense voltage is less than the polarizing voltage for either condition of switching, the preset threshold condition is maintained. The transistor therefore exhibits a non-volatile memory capability. A plurality of the transistors are employed in a memory array and may be readily fabricated in integrated circuit form.
A method of operation of a field effect transistor having source, drain, and gate electrodes and having a voltage threshold of conduction variable between first and second stable threshold conditions, comprising: providing polarizing voltages of predetermined amplitude and polarity; applying a first polarizing voltage between the gate and source electrodes of said transistor to cause said transistor to assume a first stable voltage threshold condition while maintaining said drain electrode at a potential level equal in voltage but opposite in polarity to said polarizing voltage, thereby to cause said transistor to assume a first predetermined voltage threshold condition; and while maintaining the drain electrode at said aforesaid potential; and while applying a second polarizing voltage to said gate electrode of substantially the same potential and polarity as that of said drain potential, selectively applying a negative voltage of substantially one-half of said drain potential to said source electrode to cause said transistor to retain said first stable threshold condition, and applying ground potential to said source electrode to switch said transistor to said second stable voltage threshold condition.
Claim 2
Independent Claim
178 words
A method of operation of a field effect transistor having source, drain, and gate electrodes and having a voltage threshold of conduction variable between first and second stable threshold conditions, comprising: providing polarizing voltages of predetermined amplitude and polarity; applying a first polarizing voltage between the gate and source electrodes of said transistor to cause said transistor to assume a first stable voltage threshold condition while maintaining said drain electrode at a potential level equal in voltage but opposite in polarity to said polarizing voltage, thereby to cause said transistor to assume a first predetermined voltage threshold condition; and while maintaining the drain electrode at said aforesaid potential; and while applying a second polarizing voltage to said gate electrode of substantially the same potential and polarity as that of said drain potential, selectively applying a negative voltage of substantially one-half of said drain potential to said source electrode to cause said transistor to retain said first stable threshold condition, and applying ground potential to said source electrode to switch said transistor to said second stable voltage threshold condition.
Claim 3
Dependent Claim
65 words
The method of operation of a transistor as recited in claim 1 wherein said first predetermined stable voltage threshold condition is of a lower threshold voltage than said second threshold condition, further comprising applying a voltage exceeding said first stable threshold voltage to said gate electrode, and applying a voltage greater than that of said first threshold condition to the gate electrode of said transistor.