In a semiconductor device having SiC vertical trench MOSFETs, it is aimed to prevent the generation of large scattering in the channel resistance without largely increasing the average value of channel resistance. A 4H-SiC substrate having a major face thereof that is generally a {0001} face and having an off angle .alpha.. The trench is formed with the standard deviation .sigma. in scattering of the angle formed by a trench side wall face and a substrate major face within a wafer face. By setting the designed value of the angle formed by the trench side wall face and the substrate major face at an any angle ranging from [(60 degrees)+2.sigma.] to [(90 degrees)-tan.sup.-1 (0.87.times.tan .alpha.)-2.sigma.] in forming the trench in the SiC substrate, a semiconductor device in which the angle formed by the trench side wall face and the substrate major face is 60 degrees or more but not more than [(90 degrees)-tan.sup.-1 (0.87.times.tan .alpha.)] can be obtained.