Ceramic metal circuit board and semiconductor device using the same

A ceramic metal circuit board comprising:

• a ceramic substrate;
• and
• first and second metal plates bonded to first and second opposite surfaces, respectively, of the ceramic substrate through respective bonding layers, the first and second metal plates each being made of a material selected from the group consisting of copper and a copper alloy;
• a metal film on a surface of the first metal plate that is opposite the ceramic substrate;
• and
• at least a part of a surface of the second metal plate that is opposite the ceramic substrate is not provided with the metal film;
• and
• a semiconductor element or a metal terminal mounted to the at least a part of the surface of the second metal plate that is provided with no metal film with lead-free solder, wherein:
• the maximum height surface roughness Rz of the surface of the first metal plate, the second metal plate, or both, that is provided with the metal film is 1.5 μm or less,
• a thickness of the metal film is 10 μm or less on average,
• average crystal grain sizes of the first metal plate and the second metal plate each is 200 μm or more, and
• one of the metal plates on which the metal film is provided includes a recrystallized structure.