Over the years, it has become commonplace to perform various forms of manual intervention ondesigns generated using automated flows. The quest to overcome the limitations of standard-cell-based design methods leads naturally to the creation of new design- and context-specific cells—designated flex cells--during the process of optimizing a given digital design. Flex cell—based design optimization automates the creation of tactical cells.

The flex-cell approach, either alone or in combination with standard cells, provides an optimally tuned set of building blocks for the target IC design, which measures optimality against accepted and quantifiably definable metrics such as clock speed, die size, and power consumption. By allowing manipulation of the transistor-level structures, flex cells open up a new dimension in theoptimization of automatically created designs.