Defects caused by 15R polytype inclusions in 4H silicon carbide ingots have been considered. Growth rate along with curvature of the interface determines the stability of the 4H-polytype reproduction. The domain structure arising in the 4H polytype as a result of foreign polytype inclusion has been analyzed. Antiphase domains of the 4H polytype emerging at the top and lateral sides of 15R inclusion form a strictly determined set of binary and ternary joints (extended threading defects). Junctions of a higher order could generate open-core threading superdefects. (C) 2010 Elsevier B.V. All rights reserved.