Embodiments of a stack package may include an upper chip on a lower chip, a backside passivation layer covering the backside surface of the lower chip and having a thickness which is substantially equal to a height of the protrusion portion of a lower through via electrode, a backside bump substantially contacting the protrusion portion, and a front side bump electrically connected to a chip contact portion of the upper chip and physically and electrically connected to the backside bump. The backside passivation layer may include a first insulation layer provided over a sidewall of the protrusion portion and the backside surface of the lower chip. Embodiments of fabrication methods are also disclosed.