A common failure mechanism in bulk CMOS integrated circuits is the latch-up of parasitic SCR structure inherent in the bulk CMOS structure. Latch-up triggering and holding charac-teristics have been measured in the test devicrs which include conventional and Schottky-damped CMOS structures with various well depths and n+/p+ spacings. It is demonstrated that Schottky-clamped CMOS is more latch-up immune than conventional bulk CMOS. Finally, the simulation results by circuit simulation program (SPICE) are compared with measured results in order to verify the validity of the latch-up modal composed of nan, pnp transistors and two external resistors.