Successful operation of 4H-silicon carbide (SiC) MOSFET and integrated electronic circuit based on 4H-SiC MOSFET is reported at temperature up to <inline-formula> <tex-math notation="LaTeX">500~^{\circ }\text{C} </tex-math></inline-formula> in air. The high-temperature operation of the integrated circuit (IC) based on 4H-SiC MOSFET strongly depends on the reliability of metal/SiC contact. Based on the transfer length method (TLM), the Ni/Nb/n-type 4H-SiC junction exhibits ohmic behavior with specific contact resistance of <inline-formula> <tex-math notation="LaTeX">1.86\times 10^{-{4}}\,\, \Omega \cdot </tex-math></inline-formula>cm 2 when operating at <inline-formula> <tex-math notation="LaTeX">500~^{\circ }\text{C} </tex-math></inline-formula>. In contrast, the voltage gain of the amplifier is strongly governed by the variation of carrier mobility of the 4H-SiC MOSFET when temperature varies from room temperature to <inline-formula> <tex-math notation="LaTeX">500~^{\circ }\text{C} </tex-math></inline-formula>. The experimental results show that, when the temperature is increased from <inline-formula> <tex-math notation="LaTeX">20~^{\circ }\text{C} </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">300~^{\circ }\text{C} </tex-math></inline-formula>, the amplifier gain of the IC increased from 23.8 to 153.0. Though the voltage gain decreases when the temperature increases above <inline-formula> <tex-math notation="LaTeX">300~^{\circ }\text{C} </tex-math></inline-formula>, it is still higher than 50 at <inline-formula> <tex-math notation="LaTeX">500~^{\circ }\text{C} </tex-math></inline-formula>. These results indicate that integrated electronic circuits based on this 4H-SiC MOSFET technology could be potentially used for harsh environment applications.