Si-C-N　thin　films　with　smooth　surfaces　were　synthesised　by　electron　cyclotron　resonance　plasma　chemical　vapour　deposition　at　low　microwave　powers　without　heating　silicon　substrates.　Mechanical　properties　of　obtained　films　were　examined　by　nanoindentation　based　on　Oliver　and　Pharr　method.　High　elastic　recovery　was　observed.　Hardness　and　reduced　modulus　show　no　clear　relation　with　the　elastic/plastic　work　calculated　from　load-displacement　curves.　The　energy　dissipation　kept　almost　constant　with　respect　to　the　variation　of　stiffness　during　loading　and　unloading　process.　This　opens　the　possibility　of　potential　industrial　applications　due　to　the　insensitivity　of　the　deposited　films　to　external　stress.