Disclosed are fusion memory devices and methods of fabricating the same. The fusion memory device comprises a first memory device including a first substrate having active and inactive surfaces opposite to each other and a first memory cell circuit on the active surface of the first substrate, a non-memory device including a second substrate having active and inactive surfaces opposite to each other and a non-memory circuit on the active surface of the second substrate, the non-memory device being provided on the first memory device, and a second memory device on the inactive surface of the second substrate and including a second memory cell circuit different from the first memory cell circuit. The non-memory device lies between the first and second memory cell circuits and controls an electrical operation of each of the first and second memory cell circuits.