Epitaxial substrate for electronic device comprising a high resistance single crystal substrate on a low resistance single crystal substrate, and method of manufacturing

An epitaxial substrate for electronic devices, comprising:

• a substrate having a low-resistance Si single crystal substrate, a high-resistance Si single crystal substrate arranged above the low-resistance Si single crystal substrate, and a Si oxide film provided between the low-resistance Si single crystal substrate and the high-resistance Si single crystal substrate;
• a buffer as an insulating layer, arranged on the high-resistance Si single crystal substrate;
• and
• a main laminate formed by epitaxially growing a plurality of III-nitride layers on the buffer,
• wherein a lateral direction is a current flow direction in the epitaxial substrate,
• the resistivity of the low-resistance Si single crystal substrate is 100 Ω·cm or less,
• the resistivity of the high-resistance Si single crystal substrate is 1000 Ω·cm or more, and
• an impurity element of the low-resistance Si single crystal substrate is boron, and
• the high-resistance Si single crystal substrate has a thickness of more than 10 μm, and a thickness of the low-resistance Si single crystal substrate is ten times or more than the thickness of the high-resistance Si single crystal substrate.