become the stopper film for the self aligned contact sac etching of the dram part 3 and the cobalt silicide cosi film 30 the thermal silicon nitride film low pressure silicon nitride u201c lp sin u201d 33 is formed using a vertical furnace with a gas system or atmosphere of sih 4 nh 3 n 2 under a growth temperature of 700 u00b0 c a 25 nm thickness of the thermal silicon nitride film lp sin 33 must be of a significant thickness e g 25 nm to prevent local digging or pit forming by over etching due to the fluctuation in respective thicknesses of the interlayer films owing to the thermal silicon nitride film low pressure silicon nitride lp sin 33 the minimum width of the respective gaps between adjacent gate electrodes 11 to 13 in the dram part 3 where the sidewall etch back is not conducted is 70 nm for example the aspect ratio of the gap i e the depth to width ratio of a window is 4 2 for a gate electrode height of 300 nm next in fig1 b step d a bpsg film 35 of 100 nm thickness is formed for filling each such gap the growth conditions in this case are for example that teos tep teob 300180 35 mgm o 3 h 3 4000.