The theoretical analysis of microwave characteristics of the n(+)p(+)vn(+) TUNNETT diodes made of silicon carbide is carried out. The expressions for the impedance and its active and reactive components as well as expressions for the frequency range, where the negative differential resistance takes place, and the maximal frequency of oscillations are obtained for the TUNNETT diodes made of SiC. After numerical calculations, the conclusion is made that the performance potential of TUNNETTs is better than that of the other transit time devices in very high frequency range. The use of silicon carbide for the manufacture of TUNNETTs can promise better microwave parameters over the range of frequencies 100-500 GHz. (C) 2004 Elsevier Ltd. All rights reserved.