  Here we give a results of experimental study of enhancement of
superconductivity by microwave irradiation in superconducting films. An
influence of the power, frequency of microwave irradiation, as well as
temperature and width of superconducting films on behavior of experimental
dependencies of enhanced critical current and the current at which a vortex
structure of the resistive state vanishes and the phase-slip first line appears
is analyzed. The experimental studies of films with different width reveal that
the effect of superconductivity enhancement by microwave field is common and
occurs in both the case of uniform (narrow films) and non-uniform (wide films)
distribution of superconducting current over the film width. It is shown that
enhancement of superconductivity in a wide film increases not only the critical
current and the critical temperature, but also the maximum current at which the
vortex state can exist in the film. The phenomenon of superconductivity
enhancement by microwave irradiation in wide films can be described by the
Eliashberg theory, which was used to explain the same phenomenon in narrow
channels. It was experimentally found that the interval of irradiation power in
which the superconductivity enhancement was observed, became narrower with
increasing film width, what impairs the probability of its detection.
