An integrated circuit device includes a plurality of stacked circuit layers, at least one of the plurality of circuit layers including a composite interlayer insulation layer including laterally adjacent first and second insulating material regions having different mechanical strengths and dielectric properties and a plurality of circuit components disposed in the composite interlayer insulation layer. The first insulating material region may have a lower dielectric constant and a lower mechanical strength than the second insulating material region such that, for example, the first insulating material region may be positioned near signal lines or other circuit features to reduce capacitance while using the second insulating material region near a location that is susceptible to localized mechanical stress, such as a fuse location, an external connection bonding location or a scribe line location.