Embodiments of the present invention are directed to a back-end-of-line (BEOL) compatible metal-insulator-metal on-chip decoupling capacitor (MIMCAP). This BEOL compatible process includes a thermal treatment for inducing an amorphous-to-cubic phase change in the insulating layer of the MIM stack prior to forming the top electrode. In a non-limiting embodiment of the invention, a bottom electrode layer is formed, and an insulator layer is formed on a surface of the bottom electrode layer. The insulator layer can include an amorphous dielectric material. The insulator layer is thermally treated such that the amorphous dielectric material undergoes a cubic phase transition, thereby forming a cubic phase dielectric material. A top electrode layer is formed on a surface of the cubic phase dielectric material of the insulator layer.