An electronic device is provided, which includes a substrate having an electrically conductive contact pad thereon and an electrically conductive connection terminal on the contact pad. The connection terminal includes an electrically conductive pillar structure and a solder layer that extends on the pillar structure and contacts a protruding portion of a sidewall of the pillar structure. The pillar structure can include a lower pillar layer, a diffusion barrier layer on the lower pillar layer and an upper pillar layer on the diffusion barrier layer. In some additional embodiments of the invention, the protruding portion of the sidewall of the pillar structure includes an outermost portion of an upper surface of the diffusion barrier layer. This can be achieved by making a width of the diffusion barrier layer greater than a width of the upper pillar layer when viewed in transverse cross-section.