A process for producing electronic device (for example, high-performance MOS-type semiconductor device) structure having a good electric characteristic, wherein an SiO2 film or SiON film is used as an insulating film having an extremely thin (2.5 nm or less, for example) film thickness, and poly-silicon, amorphous-silicon, or SiGe is used as an electrode. In the presence of process gas comprising oxygen and an inert gas, plasma including oxygen and the inert gas (or plasma comprising nitrogen and an inert gas, or plasma comprising nitrogen, an inert gas and hydrogen) is generated by irradiating a wafer W including Si as a main component with microwave via a plane antenna member SPA. An oxide film (or oxynitride film) is formed on the wafer surface by using the thus generated plasma, and as desired, an electrode of poly-silicon, amorphous-silicon, or SiGe is formed, to thereby form an electronic device structure.