Though 15R-SiC has a large mobility for MOSFET devices. 15R-SiC wafers are difficult to obtain. In addition, a 15R-SiC substrate is said to be essential for the 15R-SiC growth. In this paper, crystal growth of 15R-SiC on the more common 4H-SiC and 6H-SiC substrates is discussed. 15R-SiC could he frown on the C-face of 4H-SiC and the Si-face of 6H-SiC. In the case of 15R-SiC and 6H-SiC substrate, growth temperatures lower than 2000 degreesC are important. However, in the case of 4H-SiC, still lower temperature (1700 similar to 1800 degreesC) were needed. To examine the thermal stability of 15R-SiC, the grown crystal was annealed at Tb=2300 similar to 2650 degreesC. However, definite polymorphic transformation was not observed. Stacking faults in the crystal grown on the (11 (2) over bar0) plane were investigated by molten KOH etching. Stacking faults in the 15R-SiC were less than in 6H-SiC. Several stacking faults tn the 15R-SiC terminated inside the crystal.