Low‐dielectric‐constant (low‐κ) materials are a critical requirement for future generations of computer microprocessors. As a unique class of porous silicas, pure silica zeolites (PSZs) have been shown to be a promising low‐κ material with excellent mechanical strength (e.g., elastic modulus of 16–18 GPa) due to their crystalline nature. In the present study, we show for the first time that higher crystallinity of spin‐on PSZ MFI films leads to lower κ values and less moisture sensitivity—two critical properties of a porous low‐κ material. We have also advanced the two‐stage synthesis method to produce zeolite nanoparticles with high yield (77 %) and a small diameter (< 80 nm). A κ value of 1.6 is obtained from the silylated highly crystalline PSZ MFI film and the κ value only increases by 12.5 % after exposure to ambient conditions for a period of 24 h.