A negative capacitance device includes a semiconductor layer. An interfacial layer is disposed over the semiconductor layer. An amorphous dielectric layer is disposed over the interfacial layer. A ferroelectric layer is disposed over the amorphous dielectric layer. A metal gate electrode is disposed over the ferroelectric layer. At least one of the following is true: the interfacial layer is doped; the amorphous dielectric layer has a nitridized outer surface; a diffusion-barrier layer is disposed between the amorphous dielectric layer and the ferroelectric layer; or a seed layer is disposed between the amorphous dielectric layer and the ferroelectric layer.