Bonded body, ceramic-copper circuit board, and semiconductor device

A bonded body, comprising:

• a ceramic substrate;
• a copper plate;
• and
• a bonding layer located on at least one surface of the ceramic substrate,
• the bonding layer bonding the ceramic substrate and the copper plate,
• the bonding layer including Ag and Ti,
• the copper plate including
• a first region separated from the bonding layer in a thickness direction,
• a second region located between the bonding layer and the first region, the second region having a higher Ag concentration than the first region, and
• a third region located between the bonding layer and the second region, the third region having a lower Ag concentration than the second region,
• wherein
• a difference between the Ag concentration of the first region and the Ag concentration of the second region is not less than 0.05 atomic %,
• a difference between the Ag concentration of the second region and the Ag concentration of the third region is not less than 0.05 atomic %, and
• the Ag concentration of the second region is not less than 0.1 atomic % and not more than 0.4 atomic %.