A semiconductor device including a field effect transistor (FET) device includes a substrate and a channel structure formed of a two-dimensional (2D) material over the substrate. Source and drain contacts are formed partially over the 2D material. A first dielectric layer is formed at least partially over the channel structure and at least partially over the source and drain contacts. The first dielectric layer is configured to trap charge carriers. A second dielectric layer is formed over the first dielectric layer, and a gate electrode is formed over the second dielectric layer.