The development of a CMOS inverter the circuit from circuit design, circuit layout and a fabricated cross-sectional point of view is shown in Fig 3.72. The formation of the various levels which make up the finished CMOS inverter has already been discussed in previous sections. A circuit designer sees things from above, and only worries about the placement of transistors, and how they will be connected together. In fact, the only factor in the actual design of the layout engineer has any choice on is the transistor width, W. All other parameters are decided before hand by the process engineer.