A thin film transistor (TFT) apparatus is disclosed, where the apparatus includes a gate comprising metal, a source and a drain, a semiconductor body, and two or more dielectric structures between the gate and the semiconductor body. In an example, the two or more dielectric structures may include at least a first dielectric structure having a first bandgap and a second dielectric structure having a second bandgap. The first bandgap may be different from the second bandgap. The TFT apparatus may be a back-gated TFT apparatus where the source is at least in part coplanar with the drain, and the gate is non-coplanar with the source and the drain.