Method of producing semiconductor element and nonvolatile semiconductor memory produced by this method

A method of producing a semiconductor element comprising:

• a process of forming a first oxide film on a semiconductor substrate,
• a process of forming a semiconductor film and an oxidation stopping film on the first oxide film,
• a process of forming an opening by patterning the oxidation stopping film,
• a process of forming an insulating local oxide film by local oxidation of a surface of the semiconductor film exposed through the opening,
• a process of removing the oxidation stopping film,
• a process of forming a floating gate of the semiconductor film remaining under the insulating local oxide film, by selective etching of the semiconductor film masked with the insulating local oxide film,
• a process of cleaning the semiconductor substrate, and
• a process of transferring the silicon substrate with the floating gate to a chemical vapor deposition device where an initial temperature is kept in a range where oxidation of a surface of the floating gate is restrained,
• a process of heating the chemical vapor deposition device from the initial temperature to a chemical vapor deposition temperature,
• a process of forming a second oxide film covering the floating gate by low pressure chemical vapor deposition, and
• a process of annealing the second oxide film in a sparse oxygen atmosphere, after the process of forming the second oxide film,
• wherein the initial temperature is in range of 400° C.±5° C. and the chemical vapor deposition temperature is in range of 750° C.±5° C.

A method of producing a semiconductor element comprising:

• a process of forming a first oxide film on a semiconductor substrate,
• a process of forming a semiconductor film and an oxidation stopping film on the first oxide film,
• a process of forming an opening by patterning the oxidation stopping film,
• a process of forming an insulating local oxide film by local oxidation of a surface of the semiconductor film exposed through the opening,
• a process of removing the oxidation stopping film,
• a process of forming a floating gate of the semiconductor film remaining under the insulating local oxide film, by selective etching of the semiconductor film masked with the insulating local oxide film,
• a process of cleaning the semiconductor substrate, and
• a process of transferring the silicon substrate with the floating gate to a chemical vapor deposition device where an initial temperature is kept in a range where oxidation of a surface of the floating gate is restrained,
• a process of heating the chemical vapor deposition device from the initial temperature to a chemical vapor deposition temperature,
• a process of forming a second oxide film covering the floating gate by low pressure chemical vapor deposition,
• wherein tetra-ethyl ortho-silicate is formed in the process of forming the second oxide film, and
• wherein the initial temperature is in range of 400° C.±5° C. and the chemical vapor deposition temperature is in range of 750° C.±5° C.