SEMICONDUCTOR DEVICE AND MANUFACTURE THEREOF

PURPOSE:To contrive the improvement in intensity of electric field against insulation breakdown and the improvement in uniformity of the film thickness, controllability, and reliability by a method wherein an insulation film is constructed of a double-layer with a CVD SiO2 film using inorganic silane and an SiO2 film thermally oxidized. CONSTITUTION:A field insulation film 11 and a gate insulation film 12 are formed by thermally oxidizing a semiconductor Si substrate 10. After a poly Si film 13 is formed over the whole surface, it is patterned so as to remain only at the position of forming a memory element. Next, the CVD SiO2 film using inorganic silane is deposited over the whole surface; thereafter, an insulation film 14 is formed by thermal oxidation. A poly Si film 17 is formed over the whole surface, and a floating gate 13a and a control gate 17a are patterned at the part of a memory element QM by etching; then, an SiO2 film 18 is thinly formed over the whole surface by thermal oxidation. The electric characteristic of the CVD SiO2 film of inorganic silane is close to that of a thermal oxide SiO2 film of single crystal silicon and keeps a high intensity of electric field against insulation breakdown; accordingly, a sufficient intensity of electric field can be obtained even when the insulation film 14 is made thinner.