3.6.3 Twin-Tub process
It is also possible to create both a p-well and an n-well for the n-MOSFET's and p-MOSFET respectively in the twin well or twin tub technology. Such a choice means that the process is independent of the dopant type of the starting substrate (provided it is only lightly doped).
Fig. 3.67 : A simplified sketch of twin-well CMOS process cross section
