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. The fin structure includes, from bottom to top, a first semiconductor fin portion, an insulator fin portion, and a second semiconductor fin portion. A lower gate structure having a first threshold voltage contacts a sidewall of the first semiconductor fin portion, and an upper gate structure having a second threshold voltage contacts a sidewall of the second semiconductor fin portion.