We discuss the design and implementation of thin film superconducting
coplanar waveguide micro- resonators for pulsed ESR experiments. The
performance of the resonators with P doped Si epilayer samples is compared to
waveguide resonators under equivalent conditions. The high achievable filling
factor even for small sized samples and the relatively high Q-factor result in
a sensitivity that is superior to that of conventional waveguide resonators, in
particular to spins close to the sample surface. The peak microwave power is on
the order of a few microwatts, which is compatible with measurements at ultra
low temperatures. We also discuss the effect of the nonuniform microwave
magnetic field on the Hahn echo power dependence