Abstract: There is disclosed a hexagonal Group III-V nitride layer exhibiting high quality crystallinity capable of improving the properties of a semiconductor device such as a light emitting element. This nitride layer is a Group III-V nitride layer belonging to hexagonal crystal formed by growth on a substrate having a different lattice constant, which has a growth-plane orientation of {1-100} and in which a full width at half maximum b1 of angle dependence of X-ray diffraction intensity in a {1-210} plane perpendicular to the growth-plane upon X-ray incident angle from a direction parallel to the growth-plane satisfies the condition of 0.01°?b1?0.5°, or the full width at half maximum b2 of angle dependence of X-ray diffraction intensity in a {0001} plane upon X-ray incident angle from a direction parallel to the growth-plane satisfies the condition of 0.01°?b2?0.5°.