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