Depolarization field in metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with a ferroelectric-electrode interface layer was derived theoretically in this work. The polarization relaxation characteristics were investigated in details based on Lou's polarization retention model. It is found that the retention time of ferroelectric field-effect transistors (FETs) can be affected significantly by the dielectric constant and the thickness of ferroelectric thin film, and by the interface layer thickness. The results may provide some insights into the design and the retention property improvement of MFIS-FET as nonvolatile memory. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.