Its well known that all gates can be derived from NAND and NOR gates...But is it that in all digital IC's are other gates like AND ,OR and XOR gates are made up of NAND and NOR gates... does the other gates have seperate circuit using less number of transistors...
You don't have always to design your gates using NAND and NOR gates .Different CMOS families like standard CMOS ,Pseudo NMOS ,dynamic CMOS ...etc allow you to design several complex gates .Actually, gates like XOR are usually designed directly as a complex gate than using NANDs and NORs .
"digital integrated circuits: a design perspective" by rabaey .
"Microelectronic circuits" By Sedra also contains a chapter about Digital CMOS electronics .