Method of fabricating a semiconductor device with multiple gate oxide thicknesses

A method of fabricating a semiconductor device containing a plurality of transistors, the method comprising:

• forming insulation regions in a surface of a semiconductor substrate to isolate a plurality of active regions in which transistors are to be formed;
• depositing an oxide layer on first, second and third active regions;
• selectively removing the deposited oxide layer from the second and third active regions;
• thermally oxidizing the substrate to form a first thermal oxide layer, at a second thickness less than the first thickness, on the second and third active regions;
• selectively removing the first thermal oxide layer from the third active region;
• and
• thermally oxidizing the substrate surface to form a second thermal oxide layer, at a third thickness, less than the first thickness, on the third active region.

A method of manufacturing a semiconductor device containing a plurality of transistors with different gate oxide thicknesses on a substrate surface, the method comprising:

• depositing a first oxide layer on a plurality of active regions in which the transistors are to be formed;
• selectively removing the deposited first oxide layer from at least one active region leaving the first deposited oxide layer on a first active region;
• thermally oxidizing the substrate to form a thermal oxide layer on the at least one active region;
• depositing a second oxide layer on the first deposited oxide layer in the first active region, on a second active region and on the at least one active region after selectively removing the deposited first oxide layer and before thermally oxidizing to form the thermal oxide layer;
• and
• selectively removing the deposited second oxide layer from the at least one active region, leaving the deposited second oxide layer on the deposited first oxide layer and on the second active region before thermally oxidizing to form the thermal oxide layer.

A method of manufacturing a semiconductor device containing a plurality of transistors with different gate oxide thicknesses on a substrate surface, the method comprising:

• depositing a first oxide layer on a plurality of active regions in which the transistors are to be formed;
• selectively removing the deposited first oxide layer from at least one active region leaving the first deposited oxide layer on a first active region;
• thermally oxidizing the substrate to form a thermal oxide layer on the at least one active region;
• depositing at least one additional oxide layer, after selectively removing the deposited first oxide layer, and before thermally oxidizing the surface;
• and
• selectively removing the at least one additional oxide layer from the at least one active region before thermally oxidizing.

A method of manufacturing a semiconductor device containing a plurality of transistors with different gate oxide thicknesses on a substrate surface, the method comprising:

• depositing a first oxide layer on a plurality of active regions in which the transistors are to be formed;
• selectively removing the deposited first oxide layer from at least one active region leaving the first deposited oxide layer on a first active region;
• thermally oxidizing the substrate to form a thermal oxide layer on the at least one active region;
• selectively removing the thermal oxide layer from other active regions leaving the thermal oxide layer on the at least one active region;
• and
• thermally oxidizing the substrate to form another thermal oxide layer on the thermal oxide layer on the at least one active region and on the other active regions.