<p>Disclosed is an aluminum nitride circuit substrate comprising an aluminum nitride plate and a conductive material bonded to the aluminum nitride plate through a metallized layer formed on the bonding surface of the aluminum nitride plate, the conductive material being of a metallic material which has a thermal expansion coefficient of 2 x l0<-><6> to 6 x l0<-><6>/ DEG C. The aluminum nitride circuit substrate according to this invention is free from the generation of crack caused by the difference of the thermal expansion coefficients of AlN plate and a conductive material bonded to the AlN plate to improve the reliability of the elements.</p>
