A 3D multi-bit flip-flop may include a two tier structure. The two tier structure may include a first tier containing a common clock circuit for the multi-bit flip-flop as well as the clock driven portions of the individual flip-flops and a second tier containing a common scan circuit for the multi-bit flip-flop as well as the non-clock driven portions of the individual flip-flops. Alternatively, the first tier may include the common clock circuit as well as a portion of the individual flip-flops and the second tier may include the common scan circuit as well as the other portion of the individual flip-flops.