Semiconductor substrate manufacturing method

A method for manufacturing a semiconductor substrate, comprising:

• epitaxially growing a columnar group III nitride semiconductor single crystal on a principal plane of a circular substrate;
• forming a cylindrical cavity in the group III nitride semiconductor single crystal to separate the group III nitride semiconductor single crystal into a hollow cylindrical region at an outer peripheral edge side of the group III nitride semiconductor single crystal and a solid columnar region at an inside of the hollow cylindrical region of the group III nitride semiconductor single crystal;
• and
• slicing the solid columnar region after separating the group III nitride semiconductor single crystal into the hollow cylindrical region and the solid columnar region,
• wherein the forming of the cavity is carried out such that a shape of the group III nitride semiconductor single crystal always keeps an axial symmetry that a central axis of the semiconductor crystal is defined as a symmetry axis.