The present invention is effective if any one of the following gas or {TAIL ~ their mixture gas} is introduced at the time of forming the surface layer: raw material gas containing nitrogen atoms, such as nitrogen or ammonia gas; raw material gas containing oxygen atoms, such as oxygen , nitrogen monoxide , nitrogen dioxide , dinitrogen monoxide , {HEAD ~ carbon monoxide} or carbon dioxide gas; and dopant gas such as diborane , boron fluoride or phosphine gas 
The present invention is effective if any one of the following gas or { TAIL ~ their mixture gas } is introduced at the time of forming the surface layer : raw material gas containing nitrogen atoms , such as nitrogen or ammonia gas ; raw material gas containing oxygen atoms , such as oxygen , nitrogen monoxide , nitrogen dioxide , dinitrogen monoxide , { HEAD ~ carbon monoxide } or carbon dioxide gas ; and dopant gas such as diborane , boron fluoride or phosphine gas
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