A programmable metallization device comprises a first electrode and a second electrode, and a first dielectric layer, a second dielectric layer, and an ion-supplying layer in series between the first and second electrodes. In operation, a conductive bridge is formed or destructed in the first dielectric layer to represent a data value. During read, a read bias is applied that is sufficient to cause formation of a transient bridge in the second dielectric layer, and make a conductive path through the cell if the bridge is present in the first dielectric layer. If the bridge is not present in the first dielectric layer during the read, then the conductive path is not formed. Upon removal of the read bias voltage any the conductive bridge formed in the second dielectric layer is destructed while the conductive bridge in the corresponding other first dielectric layer, if any, remains.