In this letter, we report the observation of N-shaped negative-differential-resistance (NDR) characteristics in a SiC/Si heterostructure diode. The typical NDR in this device has a peak-to-valley current ratio (PVCR) of 44 and a high peak current of 4.8 mA at room temperature. A possible model based on the multi-tunneling process was proposed to explain the origin of the NRD in this device. The most attractive feature of this device is its high-temperature NDR characteristics. An obvious NDR with a PVCR of as high as 9 is obtained at 200 °C, indicating that this SiC/Si heterostructure NDR diode is promising for high-temperature electronic applications. ©1998 American Institute of Physics.