A semiconductor substrate of an embodiment includes a SiC layer having a surface inclined in a direction plus or minus 5° from a {0001} face at an off angle of 0° to 10°. Area density of threading edge dislocation clusters in the SiC layer is 18.8 cm−2 or less, each of the threading edge dislocation clusters includes a plurality of threading edge dislocations on the surface, the threading edge dislocations included in each of the threading edge dislocation clusters exist in a region that extends in a [1-100] direction plus or minus 5° and has a width of 30 μm or less, each of the threading edge dislocation clusters includes at least three threading edge dislocations adjacent at an interval of 30 μm or less, and an interval of adjacent threading edge dislocations in each of the threading edge dislocation clusters is 70 μm or less.