The integration of 2D materials in solid-state electronic devices and circuits suffers from the problematic interaction between 2D materials with adjacent 3D dielectrics in electronic devices, which results in a faster device degradation. Here we demonstrate that ultra-thin calcium fluoride (CaF2) ionic crystals could be an excellent solution to mitigate this problem. By applying over 3000 ramped voltage stresses and collecting several current maps at different locations of the samples via conductive atomic force microscopy, it is statistically demonstrated that ultra-thin CaF2 shows much better dielectric performance (i.e., homogeneity, leakage current, and dielectric strength) than SiO2, TiO2, and h-BN.