Film forming method and film forming apparatus

A film forming method of forming a SiOC-based film, the film forming method comprising:

• preparing a substrate;
• forming a SiC-based film on the substrate by using a carbon precursor which is trimethylsilyacetylene (TMSA) or [(trimethylsilyl) methyl]acetylene (TMSMA) having a triple bond between carbon atoms as an unsaturated carbon bond and a silicon precursor made of a silicon-containing gas;
• forming the SiOC-based film by performing an oxidation process on the SiC-based film on the substrate;
• and
• performing a processing with plasma of a gas containing a H2 gas on the SiOC-based film on the substrate,
• wherein the forming the SiC-based film is performed before the SiC-based film has a first given film thickness,
• wherein the forming the SiC-based film and the forming the SiOC-based film by the oxidation process are executed once or multiple times before the SiOC-based film has a second given film thickness,
• wherein an operation of forming the SiOC-based film to have the second given film thickness and the performing the processing with the plasma are executed once or multiple times,
• wherein a wet etching resistance and a composition of the SiOC-based film are controlled by adjusting the second given film thickness, and
• wherein the first given thickness of the SiC-based film is below 1.6 Å such that the SiOC-based film formed on the substrate has a leakage value of 1λ10−8 A/cm2 or less when an electric field strength of 2 MV/cm is applied.