Described is a ferroelectric-based capacitor that improves reliability of a ferroelectric memory by providing tensile stress along a plane (e.g., x-axis) of a ferroelectric or anti-ferroelectric material of the ferroelectric/anti-ferroelectric based capacitor. Tensile stress is provided by a spacer comprising metal, semimetal, or oxide (e.g., metal or oxide of one or more of: Al, Ti, Hf, Si, Ir, or N). The tensile stress provides polar orthorhombic phase to the ferroelectric material and tetragonal phase to the anti-ferroelectric material. As such, memory window and reliability of the ferroelectric/anti-ferroelectric oxide thin film improves.