Highly-oriented diamond film, method for manufacturing the same, and electronic device having highly-oriented diamond film

A highly-oriented diamond film comprising a first diamond layer deposited by {111} sector growth and a second diamond layer deposited on the first diamond layer by {100} sector growth so that the crystal grain sizes increase with distance from the first diamond layer, wherein

• an average crystal grain size of the second diamond layer at the surface is represented by Da (μm);
• an average crystal grain size of the first diamond layer at the boundary of the first diamond layer and the second diamond layer or an average crystal grain size of the first diamond layer at a cross-section being the closest to the boundary and parallel to the surface of the second diamond layer when the boundary is not parallel to the surface of the second diamond layer is represented by Db (μm);
• and a distance from the surface of the second diamond layer to the boundary or the cross-section is represented by L (μm), wherein
• a grain-size-increasing rate M (%) that is calculated by the following mathematical formula:
• M={(Da−Db)/L}×100
• is 50% or higher.