The instant invention is a process for planarizing a microelectronic substrate with a cross-linked polymer dielectric layer, comprising the steps of: (a) heating such a substrate coated with a layer comprising an uncured cross-linkable polymer and a glass transition suppression modifier to a temperature greater than the glass transition temperature of the layer, the temperature being less than the curing temperature of the uncured cross-linkable polymer to form a substrate coated with a heat flowed layer; and (b) heating the substrate coated with the heat flowed layer to a curing temperature of the uncured cross-linkable polymer of the heated layer to cure the uncured cross-linkable polymer to form a planarized substrate wherein the percent planarization at 100 micrometers is greater than fifty percent. The instant invention is a microelectronic device made using the above-described process. The instant invention is a composition of matter, comprising: an essentially solvent free composition comprising an uncured cross-linkable polymer and a glass transition suppression modifier, the composition having a glass transition temperature sufficiently less than the curing temperature of the uncured composition so that if the uncured composition is heated to a temperature above its glass transition temperature but below its curing temperature, the uncured composition will flow.