Sti (shallow trench isolation) structures for minimizing leakage current through drain and source silicides

A method for forming shallow trench isolation structures, the method including the steps of:

• A. etching a pair of isolation trenches with each isolation trench being etched through a first layer of silicon nitride and a silicon semiconductor substrate, said first layer of silicon nitride being deposited on said silicon semiconductor substrate;
• B. filling said pair of isolation trenches with silicon dioxide, said silicon dioxide extending up to fill said isolation trenches through said first layer of silicon nitride, said step B further including the step of:
• growing a liner silicon dioxide on sidewalls of said isolation trenches having exposed silicon of said semiconductor substrate;
• C. etching away said first layer of silicon nitride after said step B such that sidewalls of said silicon dioxide filling said isolation trenches are exposed beyond the top of said silicon semiconductor substrate;
• D. conformally depositing a second layer of silicon nitride on exposed surfaces of said silicon dioxide filling said isolation trenches and on said silicon semiconductor substrate;
• E. anisotropically etching said second layer of silicon nitride such that silicon nitride remains at sidewalls of said silicon dioxide filling said isolation trenches and exposed beyond the top of said silicon semiconductor substrate, wherein silicon nitride has a different etch rate in an acidic solution from silicon dioxide filling said isolation trenches;
• and
• G. forming a field effect transistor in an active device area between said pair of isolation trenches in said silicon semiconductor substrate, wherein a drain silicide and a source silicide of said field effect transistor abuts said silicon nitride on said sidewalls of said silicon dioxide filling said isolation trenches.