Highly-oriented diamond film field-effect transistor

A highly-oriented diamond film field-effect transistor, comprising;

• a source electrode,
• a drain electrode,
• a gate electrode,
• a first semiconducting diamond film connected to said source electrode,
• a second semiconducting diamond film connected to said drain electrode and having the same conductivity type as said first semiconducting diamond film,
• a highly resistant diamond film connected to said gate electrode and positioned between said first and second semiconducting diamond films, said highly resistant diamond film having a thickness in a direction between said first and second semiconducting diamond films of 10 .ANG. to 1 mm and an electrical resistance of 10.sup.2 .OMEGA..cm or more,
• a channel region being defined within said highly resistant diamond film, said channel region connecting said first and second semiconducting diamond films, and
• at least part of said first and second semiconducting diamond films and said highly resistant diamond film being made of a highly-oriented diamond film in which at least 80% of a film surface consists of a plurality of diamond crystals with (100) crystal planes, and the differences {.DELTA..alpha., .DELTA..beta., .DELTA..tau.} of the Euler angles {.alpha., .beta., .tau.}, which represent the orientations of the crystals with the (100) crystal planes, satisfy .vertline..DELTA..alpha..vertline..ltoreq.10.degree., .vertline..DELTA..beta..vertline..ltoreq.10.degree., and .vertline..DELTA..tau..vertline..ltoreq.10.degree. between adjacent (100) crystal planes.