Reviews the use of cell libraries and assembly tools for application-specific integrated circuits (ASIC's). To illustrate the design process the authors describe the construction of cells suitable for 1.2-3- mu m CMOS and BiCMOS IC's, and the use of silicon assembly tools for use with these libraries. The digital library discussed was developed from an existing set of 3- mu m standard cells, data-path cells, and logic macrocells which were modified and augmented with analog cells. The library is compatible with public-domain software for logic synthesis, place and route, simulation, and layout. The authors compare the use of these tools with other commercial systems suitable for mixed analog/digital CMOS IC design. Analog library construction utilizes a set of prototype tools to reduce the time spent in the design, layout, and simulation cycle. The authors compare and contrast this approach to the use of analog compilation tools to assemble analog layout directly. They review present and suggest new techniques to realize high-performance analog circuits for mixed analog/digital IC's.