We investigate THz response of split-ring resonator prepared on the polyimide film grown on the Si substrate. We observe a strong thickness dependence of the resonance frequency which is attributed to the change in the effective dielectric constant. From the finite-difference time-domain simulation, we reproduce experimental results, and find large variations of the electric field profile depending on the polyimide thickness. We discuss the optimal film configuration to achieve the large enhancement of THz electric field which depends strongly on thicknesses and optical constants of constituent layers. (C) 2015 Elsevier B.V. All rights reserved.