Diamond substrate and method for manufacturing diamond substrate

A method of manufacturing a diamond substrate, comprising:

• preparing a base substrate;
• forming a diamond layer formed from diamond single crystals on one side of the base substrate;
• removing a part of the diamond layer to leave a plurality of pillar-shaped diamonds from the diamond layer, the plurality of pillar-shaped diamonds being spaced apart to each other;
• causing the diamond single crystals to grow from tips of each pillar-shaped diamond while a space between the plurality of pillar-shaped diamonds are not fully filled and coalescing each of the diamond single crystals grown from the tips of each pillar-shaped diamonds to form a diamond substrate layer;
• separating the diamond substrate layer from the base substrate;
• and
• manufacturing the diamond substrate from the diamond substrate layer,
• wherein a curvature of a crystal plane in an interior of the diamond substrate is set to higher than 0 km−1 and equal to or lower than 1500 km−1.