US Patent 10998444 Stacked FinFET masked-programmable ROM

A stacked FinFET mask-programmable read only memory (ROM) is provided. The stacked FinFET mask-programmable ROM includes a fin structure extending upward from an insulator layer. In accordance with the present application, the fin structure includes, from bottom to top, a lower programmable semiconductor fin portion having a first threshold voltage, an insulator fin portion, and an upper programmable semiconductor fin portion having a second threshold voltage. A lower gate structure contacts a sidewall of the lower programmable semiconductor fin portion, and an upper gate structure contacts a sidewall of the upper programmable semiconductor fin portion.