Ceramic circuit board and semiconductor module

A ceramic circuit board comprising:

• a ceramic substrate with a 1.0 mm thickness or less, the substrate including a first surface and a second surface, the first surface including a first area and a second area;
• a first metal plate joined to the first area with a first joining layer therebetween;
• and
• a second metal plate joined to the second surface with a second joining layer therebetween,
• wherein the first surface extends along a first direction and a second direction across the first direction,
• wherein the second area has a first waviness profile along a first side in the first direction of the first surface, the first waviness profile having one extreme value or less,
• wherein the second area has a second waviness profile along a second side in the second direction of the first surface, the second waviness profile having not less than two nor more than three extreme values,
• wherein the first joining layer has a first protrusion provided on the first surface and extending from a first interface between the first joining layer and the first metal plate, the first protrusion has a length of 10 μm or more and 100 μm or less, and the first interface and a side surface of the first metal plate define a first angle of 80 degrees or less therebetween, and
• wherein the second joining layer has a second protrusion provided on the second surface and extending from a second interface between the second joining layer and the second metal plate, the second protrusion has a length of 10 μm or more and 100 μm or less, and the second interface and a side surface of the second metal plate define a second angle of 80 degrees or less therebetween.