In this study, we present a detailed EDMR study on p-channel 4H-SiC MOSFETs with dry oxidized. The dry-oxide MOSFETs showed the most degraded performance: its maximum field-effect mobility is 1.4 cm2V-1s-1 and threshold voltage is -17 V. An EDMR spectrum of the dry-oxide MOSFETs reveals a strong EDMR signal. We found several new carbon-related interface defects in p-channel MOSFETs, which are different from the PbC center and other interface centers detected so far. The new interface centers revealed hyperfine (HF) structures due to 13C nuclear spin, clearly indicating that their core atom is a carbon atom. We believe that a strong EDMR signal in p-channel MOSFETs mainly consists of three kinds of carbon-related defects, which we temporary call “center1,” “center2,” and “center3,” respectively.