Abstract: An apparatus and method are provided for forming a fluorine doped borophosphosilicate (F-BPSG) glass on a semiconductor device using a low pressure chemical vapor deposition process. The F-BPSG glass exhibits a substantially void-free and particle-free layer on the substrate for structures having gaps as narrow as 0.10 microns and with aspect ratios of 6:1. The reactant gases include sources of boron and phosphorous dopants, oxygen and a mixture of TEOS and FTES. Using a mixture of TEOS and FTES in a low pressure CVD process provides a F-BPSG layer having the above enhanced characteristics. It is a preferred method of the invention to perform the deposition at a temperature of about 750-850.degree. C. and a pressure of 1 to 3 torr to provide for in situ reflow of the F-BPSG during the deposition process. An anneal is also preferred under similar conditions in the same chemical vapor deposition chamber to further planarize the F-BPSG surface.