  Spin-photon coupling presents an enticing opportunity for the long-range
coupling of spin qubits. The spin-photon coupling rate $g_{s}$ is proportional
to the charge-photon coupling rate $g_{c}$. To move deeper into the strong
coupling regime, $g_{c}$ can be enhanced by fabricating high-impedance cavities
using high kinetic inductance films. Here we report dc transport and microwave
response investigations of niobium nitride (NbN) films of different
thicknesses. The kinetic inductance increases rapidly as the film thickness is
reduced below 50 nm and for 15 nm NbN films we measure a sheet kinetic
inductance $L_{k,S}$ = 41.2 pH/$\Box$. As an application of the high kinetic
inductance films, we fabricate compact LC filters that are commonly used to
reduce microwave leakage in circuit quantum electrodynamics (cQED) devices.
These filters feature up to 60 dB of attenuation near typical cavity resonance
frequencies $f_c$ = 8 GHz.
