Jerry C. Whitaker.
"Microelectronics 2nd Edition".
2005.
p. 7-7 to 7-8.
quote:
"CMOS inverters and gates inherently have ...
parasitic bipolar transistors that form a silicon controlled rectifier (SCR).
Although ... latch-up cannot be avoided,
CMOS manufacturers design input and output circuits that are latch-up resistant"