Provided are a porous organosilicate polymer composite prepared by heating an organic/inorganic hybrid polymer in which an organosilicate polymer is chemically bonded to a radial pore-forming polymer ended with a hydrolyzable alkoxysilyl group and used as a core molecule, and a semiconductor device using an organosilicate polymer composite film including the porous organosilicate polymer composite. The organosilicate polymer composite film has a very low dielectric constant, and thus, is useful as a dielectric film of the semiconductor device.