To form a flat-spin-on-glass layer with superior productivity on the surface of a semiconductor substrate having irregularities.

In this manufacturing method, spin-on-glass, which is applied on the surface of a substrate having irregularities formed on a semiconductor substrate, is baked and flattened, the spin-on-glass is formed thick at the recessed part of the irregularities, and the spin-on glass is formed thin on the protruding part of the irregularities. At his time, a first-stage roller (81) is at 150±50°C, second-stage (82) is at 250±50°C, a third-stage roller (83) is at 300±50°C, a fourth-stage roller (84) is at 350±70°C, a fifth-stage roller (85) is at 350±70°C, and a sixth-stage roller (86) is at 350±70°C. The constitution is such that the intervals between the rollers from the first stage to the sixth stage become gradually narrow.