"Super H2O-barrier film" with a water vapor transmission rate (WVTR) less than 1 mg/m(2)/day has been developed. The barrier layer is a single layer of amorphous SiCN grown by organic Cat-CVD (O-Cat-CVD) with a thickness of 100 nm. SiCN has been grown by using a gas mixture of monomethylsilane (MMS; Si (CH3)H-3), NH3 and H-2 on polyethylene-naphthalate (PEN) film substrates. It has been found that the WVTR drastically depends on the W-filament temperature of O-Cat-CVD. The WVTR changed from 5 x 10(-1) to 1 x 10(-3), corresponding to the W-filament temperature increase from 1100 to 1200 C. We have recently succeeded in developing the "super H2O-barrier film" by the coating of single layers of SiCN for both sides of the PEN film without using the widely used polymer/inorganic multilayer coating. The both-side coating has been found to be crucial to avoid the H2O penetration into PEN films and also to avoid the breakdown of the SiCN/PEN interface caused by the H2O accumulation at the interface. (C) 2011 Elsevier B.V. All rights reserved.