A method of designing a 3D Integrated Circuit, the method including: performing partitioning to at least a first strata and a second strata; then performing a first placement of the first strata using a 2D placer executed by a computer, where the 2D placer is a Computer Aided Design (CAD) tool currently used in the industry for two-dimensional devices; and performing a second placement of the second strata based on the first placement, where the partitioning includes a partition between logic and memory, and where the logic includes at least one decoder representation for the memory.