Process for depositing and planarizing bpsg for dense trench mosfet application

A process for filling a trench having sidewalls and a floor in a semiconductor device or integrated circuit, said process comprising:

• forming an insulating layer on the sidewalls and floor of a trench etched into a semiconductor substrate;
• substantially filling the trench with semiconductor material;
• removing semiconductor material from an upper portion of the trench;
• depositing a first layer of BPSG in the upper portion of the trench, said first layer of BPSG comprising boron and phosphorus in a weight ratio of boron:phosphorus of greater than 1:1;
• heating the substrate to a first temperature greater than about 850° C. and up to about 100° C.;
• depositing a second layer of BPSG above the first layer of BPSG, said second layer of BPSG comprising boron and phosphorus in a weight ratio of boron:phosphorus of greater than 1:1;
• and
• heating the substrate to a second temperature greater than about 850° C. and up to about 1100° C.