In this paper, we report the effects of bromine etch and HNO3 post-etch treatment on the C-V characteristics of MIS devices with ZnS on LPE-grown HgCdTe wafers. C-V characteristics of most devices at 1 MHz showed more increased surface doping concentrations than the original values of the wafers. These apparent doping concentrations were strongly dependent on the surface treatments. These are thought to result from the surface treatment effects on the interface trap density and the surface minority carrier response time. By longer bromine etch and by HNO3 post-etch treatment, the interface trap density decreased and the surface minority carrier response time increased.