Two different substrates and/or wells: which are p-type for NMOS
and n-type for PMOS.
Diffusion regions (p+ and n+): which defines the area where
transistors can be formed. These regions are also called active areas.
Diffusion of an inverse type is needed to implement contacts to the
well or to substrate. These are called select regions.
Transistor gate electrodes : Polysilicon layer
Metal interconnect layers
Interlayer contacts and via layers.