Self-aligned contact formation utilizing sacrificial polysilicon

A method comprising

• forming an oxide spacer layer over a substrate having patterned word line gate stacks and drain and source trenches formed therein;
• depositing a sacrificial polysilicon layer over the substrate to fill the drain and source trenches;
• etching the sacrificial polysilicon layer e so that height of the sacrificial polysilicon within the source and drain trenches is substantially equal to height of the oxide spacer layer on the wordline gate stacks;
• depositing a nitride patterning layer over the substrate;
• patterning the nitride patterning layer to define isolation regions over the drain trenches;
• etching the sacrificial polysilicon layer using the patterned nitride patterning layer to form open drain isolation regions;
• depositing an interlayer dielectric (ILD) material within the open drain isolation regions to form drain isolation plugs;
• removing the nitride patterning layer;
• etching remaining portions of the sacrificial polysilicon layer to form open drain contact regions and open source contact regions;
• etching the spacer layer below the open drain contact regions and the open source contact regions;
• and
• depositing a contact layer within the open drain contact regions and the open source contact regions to form drain contact plugs and source rail contact plugs.