We developed a novel hybrid bonding technology for Au ultralow-profiled bumps and underfill resin with a modified "lock-and-key structure." The lock structure interlocks with the key structure. We applied these structures to perform an entire adhesion between the mating surfaces in place of conventional underfilling technique. To fabricate the key structure, we developed a simple process that can remove resin on the bumps. Lock structure was fabricated by photolithography and dry etching. After the bonding was carried out, the bonded interface was observed with a Scanning Electron Microscope (SEM), a transmission electron microscope (TEM) and a Scanning Acoustic Microscope (SAM). The results proved that no significant gap was existed at both Au-Au and resin-resin interface. Furthermore, the shear strength of the bonded sample with resin was ten times stronger than that without resin. The conduction of Au bump connections after hybrid bonding was also confirmed.