<p>Provided is a semiconductor epitaxial substrate which has low semiconductor layer mosaicity and is suitable for the production of a semiconductor device. Specifically provided is a semiconductor epitaxial substrate formed by epitaxially growing a graded buffer layer which is compositionally graded such that the lattice constant increases in stages within a range from a first lattice constant to a second lattice constant larger than the first lattice constant, and a semiconductor layer produced from a semiconductor crystal having the second lattice constant on a semiconductor substrate having the first lattice constant. The angle formed by the (mnn) plane (m and n are integers except m=n=0) of the semiconductor layer and the (mnn) plane of the semiconductor substrate is set to +0.05° or more when the direction that rotates clockwise from the [100] direction to the [011] direction is positive.</p>
