We present the sensitivity improvement of total internal reflection fluorescence microscopy for imaging intracellular molecular movements near cell membranes. We investigated employing dielectric films on a prism substrate for the enhancement of fluorescence emission intensity. A two-layer dielectric thin film structure using Al2O3 and SiO2 was designed and fabricated to provide the maximal field enhancement for 442 nm excitation at a reasonable angle of incidence (). The field enhancement achieved by the design was 8.5 at = 53.8Â for TE polarization and confirmed experimentally using microbeads. Preliminary results in live cell imaging were obtained using quantum dots.