SnO 2 thin films were prepared using SnCl 4 and O 2 as precursors by means of plasma enhanced chemical vapour deposition (PECVD) method, and were modified with CuO by soaked technique to form a SnO 2 -CuO-SnO 2 sandwich structure. The sensing composite thin film sensors were proved to be highly sensitive and selective to H 2 S. Furthermore, the response and recovery speed of the thin film sensors was fairly quick.