Wafer processing

A method of forming a device comprising:

• providing a substrate having top and bottom pad stacks, wherein each pad stack comprises at least first and second pad layers, and the second pad layers of the top and bottom pad stacks comprise an initial thickness TT1 and TB1 respectively;
• forming trench isolation regions in the substrate;
• performing a removal process to completely and simultaneously remove the second pad layers of the top and bottom pad stacks from the substrate after forming the trench isolation regions;
• forming a gate dielectric layer surrounding top, bottom and side surfaces of the substrate;
• forming a protective layer over a top surface of the gate dielectric layer;
• and
• removing exposed portions of the gate dielectric layer not covered by the protective layer.