Lossy dielectrics are a significant source of decoherence in superconducting quantum
circuits. In this report, we model and compare the dielectric loss in bulk and interfacial
dielectrics in titanium nitride (TiN) and aluminum (Al) superconducting coplanar waveguide
resonators. We fabricate isotropically trenched resonators to produce a series of device
geometries that accentuate a specific dielectric region's contribution to the resonator quality
factor. While each dielectric region contributes significantly to loss in TiN devices, the metal …