Provided is a ferroelectric thin-film structure including a semiconductor substrate, a first ferroelectric layer on the semiconductor substrate, and a second ferroelectric layer on the semiconductor substrate. The second ferroelectric layer is spaced apart from the first ferroelectric layer and has a different dielectric constant from the first ferroelectric layer. The first ferroelectric layer and the second ferroelectric layer may be different from each other in terms of the amount of a dopant contained therein, and may exhibit different threshold voltages when applied to transistors.