A deposition method modulates the reaction rate and thickness of highly conformal dielectric films deposited by forming a saturated catalytic layer on the surface and then exposing the surface to silicon-containing precursor gas and a reaction modulator, which may accelerate or quench the reaction. The modulator may be added before, after, or during exposure of the silicon-containing precursor gas. The film thickness after one cycle of deposition may be increased up to 20 times or decreased up to 20 times.