Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2005-Feb-19
The storage capacity of a read-only memory (ROM) is doubled by using a field-effect transistor (FET) 1 in Fig. 1 which has an asymmetric threshold voltage. Its conduction/nonconduction is determined by the threshold voltage (Vt) at the vicinity of the source 2 not by Vt at that of the drain 3. In Fig. 2, if the gate voltage Vg to the node 10 is applied such that Vt (near the node 9) < Vg < Vt (near the node 8), current will flow from 8 to 9 but not from 9 to 8. The high Vt value (H) near the node 8 will act as a barrier to electrons from the node 8 but not from the node 9. This electron flow will be controlled by an energy barrier at the source side. The energy barrier at the drain side will give little effect to the electron flow because the drain will be biased positive. In Fig.