Abstract: This invention provides a base material with a siliceous film, which is free from voids and cracks in the interior of groove(s) in a trench isolation structure and has excellent adhesion between a substrate and a siliceous film, and a process for producing the base material with a siliceous film. A trench isolation structure is formed by a method comprising coating a silicon-containing polymer solution onto a substrate having trench isolation groove(s) of which the surface has been continuously covered with a silicon nitride liner film, and heat treating the coated substrate at a temperature of from 900° C. to 1200° C. The base material with a siliceous film is provided using the method.

Abstract: There are provided a process for producing a siliceous film having excellent insulating properties, and a coating composition for use in the process. The coating composition comprises a perhydropolysilazane or modified perhydropolysilazane having a number average molecular weight of 100 to 50,000 and an aluminum compound, the composition having an aluminum content of not less than 10 ppb and not more than 100 ppm in terms of the molar ratio of the aluminum atom to the silicon atom. The siliceous film is produced by coating the coating composition onto a substrate and firing the coated substrate in an atmosphere containing steam, oxygen, or a mixed gas composed of steam and oxygen.

Abstract: There is provided a method for trench isolation structure formation, which produces neither voids nor cracks within a groove. This method comprises the steps of: forming a groove on a surface of a silicon substrate; coating a polysilazane solution; prebaking the coating at a prebaking temperature regulated so that the temperature is raised in a temperature range of 50° C. to 400° C. over time; curing the coating at a temperature above the maximum prebaking temperature; and polishing and etching the film. The prebaking is carried out while raising the temperature either stepwise in two or more stages or in a monotonically increasing manner.