Abstract
<title>Abstract</title> <p>Barium strontium titanate (BST) thin films are promising dielectric materials for radio-frequency (RF), microwave, and integrated passive devices because of their high dielectric permittivity and excellent electrical tunability. In this work, the electrical performance of BST-based metal–insulator–metal (MIM) capacitors with dielectric thicknesses of 50, 70, and 170 nm was systematically compared with that of a 100 nm BST-based interdigital capacitor (IDC) fabricated on platinized silicon substrates. BST thin films were deposited by radio-frequency magnetron sputtering, followed by the deposition of Cr/Au (40/200 nm) electrodes using thermal evaporation. The fabricated devices were characterized through capacitance–voltage, conductance–voltage, capacitance density, dielectric constant, dielectric loss, quality factor, electric field, normalized capacitance, and frequency-dependent measurements. The 50 nm BST MIM capacitor exhibited the highest capacitance density (≈ 0.074 F m⁻²), the highest quality factor (≈ 3.1 at 1 MHz), and a maximum electric field of ≈ 6 MV cm⁻¹, whereas the 170 nm BST capacitor achieved the highest dielectric constant (≈ 1090 at 500 kHz). The dielectric loss of all the manufactured devices decreased dramatically with an increase in frequency, showing high-frequency behavior. Interdigital BST capacitor with a thickness of 100 nm showed stable capacitance and conductance with insignificant bias dependence in the studied frequency range. The study shows that the thickness of the dielectric layer and capacitor structure have a strong impact on the electrical properties of BST thin-film capacitors. Lower dielectric thickness provides better capacitance density and quality factor, while higher thickness increases the dielectric permittivity.</p>