  We report epitaxial synthesis of superconducting CsxWO3 (x = 0.11, 0.20,
0.31) films on Y-stabilized ZrO2 (111) substrates. The hexagonal crystal
structure was verified not only for composition within the stable region of
bulk (x = 0.20, 0.31), but also for the out-of-range composition (x = 0.11).
The onset of superconducting transition temperature (TC) was recorded 5.8 K for
x = 0.11. We found strong correlation between TC and c-axis length,
irrespective of the Cs content. The results indicate that hidden
superconducting phase region of hexagonal tungsten bronze is accessible by
using epitaxial synthesis of lightly doped films.
