a suitable reaction to occur in which case cooling means for the substrate has to be provided in use of the above described apparatus a substrate 10 is mounted on a substrate holder 10 39 and the reaction chamber is evacuated to 1 u00d7 10 6 torr or a higher vacuum condition then hydrogen gas isintroduced from a gas introducing system 6 at 300 sccm and microwave energy at a power level of 1 kilo watts and a frequency of 2 45 ghz is injected from the microwave generator through a microwave introduction window 15 into the plasma generating space 1 which is subjected at the same time to a magnetic field of about 2k gauss generated by the magnets 5and 5 39 the magnets are adapted to adjust the magnetic field strength the hydrogen is excited into a high density plasma state in the space 1 the surface of the substrate 10 is cleaned by high energy electrons and hydrogen atoms in addition to the introduction of hydrogen gas a productive gas comprising a carbon compound such as c 2 h 2 c 2 h 4 c 2 h 6 ch 3 oh c 2 h 5 oh or ch 4 for example is inputted at 30 sccm through a gas introduction system 7 in this process the productive gas is diluted with hydrogen at a sufficiently low density e g 1 to 5 further ni co 4 at 1 sccm and geh 4 at 2 sccm in addition if necessary as a catalyst is inputted to the reaction chamber from the introduction system the proportion of the catalyst to the carbon compound gas being 0 1 to 10 nif nio nif h 2 o n where n 1 3 ni cn 2 ni c 5.