We report a facile route to synthesize novel microstructured SiCNO films via a block copolymer micellar-templating approach, in which polyvinylsilazane (PVSZ)-swelled F127 micelles are used as a precursor and the crystallization of the PEO shell of PVSZ-swelled F127 micelles is used to control the microstructure of SiCNO films. By changing the evaporation temperature of multistep thermal treatments, SiCNO films containing nanospheres, rods, crosses, cuboids, and microspheres can be formed. We find that these microstructures have a significant effect on the dielectric loss of SiCNO films, which can be explained by the Maxwell-Wagner effects and impurities at interfaces.