Interlayer dielectric planarization process

A method of forming a planar interlayer dielectric layer over underlying structures, the method comprising:

• forming a liner oxide layer over the underlying structures;
• forming a BPSG layer over the liner oxide layer;
• planarizing said BPSG layer;
• forming a cap oxide layer over the BPSG layer;
• forming a heat dissipating layer formed from silicon nitride (Si3N4) over the cap oxide layer, said heat dissipating layer being between 300 and 1500 angstroms thick;
• forming a contact hole through said heat dissipating layer, said cap oxide layer, said BPSG layer, and said liner oxide layer down to the underlying structures;
• forming a tungsten plug in said contact hole;
• and
• forming a conductive structure over said tungsten plug and said heat dissipating layer;
• wherein said heat dissipating layer acts to conduct heat away from said conductive structure into said underlying structures.