Abstract: Embodiments herein describe techniques for a semiconductor device including a substrate and a transistor above the substrate. The transistor includes a channel layer above the substrate, a conductive contact stack above the substrate and in contact with the channel layer, and a gate electrode separated from the channel layer by a gate dielectric layer. The conductive contact stack may be a drain electrode or a source electrode. In detail, the conductive contact stack includes at least a metal layer, and at least a metal sealant layer to reduce hydrogen diffused into the channel layer through the conductive contact stack. Other embodiments may be described and/or claimed.