Embodiments herein describe techniques for a semiconductor device including a first transistor above a substrate, an insulator layer above the first transistor, and a second transistor above the insulator layer. The first transistor includes a first channel layer above the substrate, and a first gate electrode above the first channel layer. The insulator layer is next to a first source electrode of the first transistor above the first channel layer, next to a first drain electrode of the first transistor above the first channel layer, and above the first gate electrode. The second transistor includes a second channel layer above the insulator layer, and a second gate electrode separated from the second channel layer by a gate dielectric layer. Other embodiments may be described and/or claimed.