(100)-Ba0.65Sr0.35TiO3 (BST) films were deposited on Pt/Ti/SiO2/Si substrates using a low-temperature self-buffered layer. X-ray diffraction and atomic force microscope investigations show that the microstructure of BST films strongly depends on surface morphology of annealed self-buffered layer. The mechanism of nucleus formation and the growth initiation of BST films on self-buffered layers were proposed. It was found that the pyroelectric properties of BST films can be greatly enhanced. The pyroelectric coefficient and material merit figure of (100)-BST films are 1.16×104 μC m-2 K-1 and 2.18×10-4 Pa-1/2, respectively. The detectivity of 9.4×107 cm Hz1/2 W-1 was obtained in the (100)-BST film capacitors thermally isolated by 500 nm SiO2 films.