Dry etching method

A dry plasma etching method for selectively etching a silicon oxide based material layer formed on a silicon nitride based material layer, comprising

• a just etching process, using an etching gas containing at least one kind of sulfur fluoride selected from the group consisting of S.sub.2 F.sub.2, SF.sub.2, SF.sub.4 and S.sub.2 F.sub.10, and plasma etching a silicon oxide material layer substantially to thickness thereof while yielding depositable sulfur in an etching reaction system, and
• an overetching process, using an etching gas containing at least one kind of sulfur fluoride selected from the group consisting of S.sub.2 F.sub.2, SF.sub.2, SF.sub.4 and S.sub.2 F.sub.10, and a nitrogen based compound, and plasma etching a remaining portion of the silicon oxide based material layer while yielding a depositable sulfur nitride based compound in an etching reaction system.

A dry etching method for selectively etching a silicon oxide based material layer formed on a substrate, comprising

• providing a patterned layer of sulfur nitride based compound on the silicon oxide based material layer,
• carrying out a plasma etching using an etching gas containing at least one kind of sulfur fluoride selected from the group consisting of S.sub.2 F.sub.2, SF.sub.2, SF.sub.4 and S.sub.2 F.sub.10, and a nitrogen based gas, and
• while plasma etching depositing a sulfur nitride based compound on exposed portions of the silicon oxide based material layer and the substrate.

A dry plasma etching method for etching a silicon oxide based material layer with a sulfur nitride based compound layer selectively formed thereon as a mask, comprising

• a just etching process, using an etching gas containing at least one kind of sulfur fluoride selected from the group consisting of S.sub.2 F.sub.2, SF.sub.2, SF.sub.4 and S.sub.2 F.sub.10, and a nitrogen based compound, and plasma etching the silicon oxide based material layer substantially to thickness thereof while yielding depositable sulfur and sulfur nitride based compound in an etching reaction system, and
• an overetching process, using an etching gas containing at least one kind of sulfur fluoride selected from the group consisting of S.sub.2 F.sub.2, SF.sub.2, SF.sub.4 and S.sub.2 F.sub.10, and a nitrogen based compound, and plasma etching a remaining portion of the silicon oxide material layer while yielding a depositable sulfur nitride based compound in an etching reaction system.