A new switching device has been conceived and reduced to practice. Thi
s device is a once-programmable three-terminal fuse (TTF) with an on-r
esistance of a good metallic conductor and an off-resistance which is
essentially infinite. In the new structure the fusible circuit path is
fully isolated from a control electrode both before and after program
ming. We discuss the basic concept of the TTF and highlight some of it
s possible applications.