Techniques are disclosed for providing trench isolation of semiconductive fins using flowable dielectric materials. In accordance with some embodiments, a flowable dielectric can be deposited over a fin-patterned semiconductive substrate, for example, using a flowable chemical vapor deposition (FCVD) process. The flowable dielectric may be flowed into the trenches between neighboring fins, where it can be cured in situ, thereby forming a dielectric layer over the substrate, in accordance with some embodiments. Through curing, the flowable dielectric can be converted, for example, to an oxide, a nitride, and/or a carbide, as desired for a given target application or end-use. In some embodiments, the resultant dielectric layer may be substantially defect-free, exhibiting no or an otherwise reduced quantity of seams/voids. After curing, the resultant dielectric layer can undergo wet chemical, thermal, and/or plasma treatment, for instance, to modify at least one of its dielectric properties, density, and/or etch rate.