Bonding contacts having capping layer and method for forming the same

A bonded structure, comprising:

• a first bonding layer comprising a first bonding contact and a first dielectric;
• a second bonding layer comprising a second bonding contact and a second dielectric;
• and
• a bonding interface between the first bonding layer and the second bonding layer,
• wherein the first bonding contact is in contact with the second bonding contact at the bonding interface, and the first dielectric is in contact with the second dielectric at the bonding interface, and
• at least one of the first bonding contact and the second bonding contact comprises a capping layer at the bonding interface having a conductive material different from a remainder of the respective first or second bonding contact.

A method for forming a semiconductor device, comprising:

• forming a first device layer on a first substrate;
• forming a first bonding layer comprising a first bonding contact above the first device layer;
• forming a first capping layer at an upper end of the first bonding contact, the first capping layer having a conductive material different from a remainder of the first bonding contact;
• forming a second device layer on a second substrate;
• forming a second bonding layer comprising a second bonding contact above the second device layer;
• and
• bonding the first substrate and the second substrate in a face-to-face manner, so that the first bonding contact is in contact with the second bonding contact by the first capping layer.