Conductance deep-level transient spectroscopy (CDLTS) has been performed for 4H-SiC metal-semiconductor field effect transistor (4H-SiC MESFETs). Additionally to an emission band, two unexpected hole-like traps labelled HL1 and HL2 are observed in the spectra. Different measurements, varying the bias conditions show that these traps originate either from the surface state outside the gate region between gate and drain electrodes (HLI) or from interface states at the channel/buffer-layer or buffer-layer/semi-insulating substrate (HL2). The activation energies of both states are respectively determined as 0.90 eV for HLI and 0.56 eV for HL2. (c) 2005 Elsevier Ltd. All rights reserved.