  Anti-ThCr$_2$Si$_2$ type $RE_2$O$_2$Sb ($RE$ = rare earth) with Sb square net
has shown insulating conduction so far. Here we report the synthesis of
La$_2$O$_2$Sb epitaxial thin films for the first time by multilayer solid-phase
epitaxy. The valence state of Sb was about -2 evaluated from X-ray
photoemission spectroscopy measurement, and the indirect band gap of 0.17 eV
was observed. The La$_2$O$_2$Sb epitaxial thin film showed unexpectedly high
electrical conduction as a narrow gap semiconductor, whose resistivity at room
temperature was approximately ten-thousand-fold lower than that of
La$_2$O$_2$Sb bulk polycrystal, attributed to increased carrier mobility
probably due to suppressed Sb dimerization.
