A thin-film transistor photosensor and a liquid crystal display (LCD) panel respectively utilize a dielectric layer having F—SiOC: H compound and a bump structure having F—SiOC: H compound so as to form a thin-film transistor photosensor having lower resistor-capacitor loading (RC loading) and an LCD panel having low-dielectric F—SiOC: H compound respectively. In addition, a method of forming a dielectric layer having F—SiOC: H compound utilizes gases including trimethyl silane, carbon tetrafluoride, argon, and oxygen for thin-film deposition process so as to form a low-k F—SiOC: H compound dielectric layer.