Step coverage mechanisms involved in four low pressure chemical vapor deposition (LP‐CVD) processes, silicon from silane, in‐situ boron‐doped silicon from silane and boron trichloride, in‐situ phosphorus‐doped silicon from silane and phosphine, and partly oxidized silicon from silane and nitrous oxide, are studied in detail for various microscale feature shapes and dimensions. Experimental thickness profiles within trenches are compared with simulation results obtained from two diffusion‐reaction trench models developed in connection with pre‐existing reactor models. Analysis of the contribution of each reactive species to step coverage offers opportunities for progress, particularly in the design of the shape and dimensions of trenches in respect of the kinetic characteristics of each deposit.