Embodiments herein describe techniques for a semiconductor device, which may include a substrate, and a U-shaped channel above the substrate. The U-shaped channel may include a channel bottom, a first channel wall and a second channel wall parallel to each other, a source area, and a drain area. A gate dielectric layer may be above the substrate and in contact with the channel bottom. A gate electrode may be above the substrate and in contact with the gate dielectric layer. A source electrode may be coupled to the source area, and a drain electrode may be coupled to the drain area. Other embodiments may be described and/or claimed.