Epitaxial perovskite potassium tantalate (KTaO(3)) films with thicknesses of 7.4-36 nm are grown on SrTiO(3)(001) substrates by pulsed laser deposition. X-ray diffraction (XRD) analysis reveals evolution of lattice strain with increasing film thickness. A biaxial compressive in-plane strain as large as - 2.1% is obtained in the 7.4 nm-thick film. A bi-layer microstructure is detected in the 18 nm-thick film, suggesting the possibility for an abrupt strain relaxation.