Low temperature carbon rich oxy-nitride for improved RIE selectivity

A method of forming a self-aligned feature comprising:

• providing a multiplicity of gate stack depositions;
• depositing a spacer nitride against a multiplicity of sides of each of said multiplicity of gate stacks;
• depositing at a temperature between 500° C. and 700° C. a layer of silicon oxy nitride containing carbon over all exposed surfaces, wherein said carbon is evenly distributed throughout said silicon oxy nitride;
• depositing boro phospho silicate glass (BPSG) filling a height above said gate-stack deposition;
• chemical mechanical polishing said BPSG;
• depositing oxide and annealing;
• depositing a mask on said oxide;
• etching a contact hole in said oxide through a portion of said gate stack to a first depth;
• etching said contact hole further in said Silicon dioxide through a width of said nitride spacer to a second depth;
• filling said contact hole with polysilicon;.
• etching a bitline trench in said oxide;
• and
• filling said bitline trench with metal.