A possible explanation for these results is a gas trapping effect, where the precursors are trapped in the lower part of the trenches, rendering a local continuous CVD leading to a higher SC. The GPC with 1 s purge in the lower part of trenches (black solid line in Figure (a)) seems to be independent of the trench width, while the GPC with 5 s purge in the lower part of the trench decreases with decreasing trench width (red solid line in Figure (a)). Since a gas trapping effect should be more pronounced in a narrower trench, resulting in a higher GPC in the lower part of the trenches with smaller widths, these results speak against a gas trapping effect. The average GPC at the lower part of the trenches is higher with 5 s purge compared with 1 s purge, which further contradicts the gas trapping effect as a longer gas purge would aid in removing the residual precursor molecules from the trenches. These effects increase the partial pressure of HCl closer to the trench opening, resulting in a higher inhibition effect and a lower GPC in the upper part of the trenches, as seen in Figure . In a continuous CVD process, both Si-and C-precursor molecules arrive at the surface at a similar rate, leading to a mix of surface species. In our pulsed CVD process, only Si-or C-precursors arrive at the surface during a precursor pulse. During the Si pulse, it is expected that the whole surface is covered with SiClx species, rendering a stronger inhibition effect compared to a continuous CVD process, where there is a more even mixture of SiClx and CHx surface species. This would explain the extremely high SC values of up to 9.