Controlling the reflow behaviour of BPSG films and devices made thereof

A method for depositing an insulating layer includes performing a primary deposition over a sidewall of a feature by depositing a layer of silicate glass using a silicon source at a first flow rate and a dopant source at a second flow rate. A ratio of the flow of the dopant source to the flow of the silicon source is a first ratio. The method further includes performing a secondary deposition over the sidewall of a feature by increasing the flow of the silicon source relative to the flow of the dopant source. The ratio of the flow of the dopant source to the flow of the silicon source is a second ratio lower than the first ratio, and stopping the flow of the silicon source after performing the secondary deposition. A reflow process is performed after stopping the flow. A variation in thickness of the layer of silicate glass over the sidewall of a feature after the reflow process is between 1% to 20%.