Methods of fabricating semiconductor devices and resulting bonded structures. An embodiment method includes tilting a plasma nozzle to an angle with respect to a substrate. The method includes applying, with the plasma nozzle, an oxidation gas onto a first side of at least one substrate-side copper bump on the substrate, forming an oxidized copper sidewall on the first side of the substrate-side copper bump. The method includes bonding a semiconductor chip to the substrate using the substrate-side copper bump.

A semiconductor package includes a first semiconductor chip having a first front surface and a first back surface opposing each other, and including first front connection pads, first back connection, and through-electrodes, a second semiconductor chip having a second front surface facing the first back surface and including second front connection pads, a substrate having a third back surface facing the first front surface and including upper pads and lower pads disposed opposite to each other, first bump structures between the first semiconductor chip and the second semiconductor, second bump structures between the first semiconductor chip and the substrate, and connection bumps. A first gap between the second front surface and the first back surface is equal to or greater than a second gap between the first front surface and the third back surface, and the second gap is greater than a thickness of the first semiconductor chip.