Boron nitride (BN) films are synthesized using BCl3 and N-2 as source gases by plasma-assisted chemical vapor deposition. The BN film consists of hexagonal grains of 3 nm in size. The energy gap is estimated to be as wide as 6.0 eV from ultraviolet-visible optical transmission measurement. The electrical resistivity is estimated to be 2 x 10(11) and 1.3 x 10(2) Omega cm for undoped and sulfur-doped BN films, respectively. The electron emission current is detected at electric fields higher than 9 V/mu m. The tunneling barrier height is estimated to be 0.1 eV from the Fowler-Nordheim plot. BN;coated Si tip field emitter arrays are fabricated. The electron emission occurs at electric field as low as 6 V/mu m. It is demonstrated that the electron emission characteristic of Si tip array is much improved by BN coating.