A full fill trench structure is described, including a microelectronic device substrate having a high aspect ratio trench therein and filled with silicon dioxide of a substantially void-free character and substantially uniform density throughout its bulk mass. A method of manufacturing a semiconductor product also is described, involving use of specific silicon precursor compositions for forming substantially void-free and substantially uniform density silicon dioxide material in the trench. The precursor fill composition may include silicon and germanium, to produce a microelectronic device structure including a GeO2/SiO2 trench fill material. A suppressor component may be employed in the precursor fill composition, to eliminate or minimize seam formation in the cured trench fill material.