NOVELTY - Silicon precursor composition comprises a silylene compound selected from silylene compounds.    USE - The silicon precursor composition and methods are useful for forming silicon-containing film on substrate; maintaining amorphous character of amorphous hafnium oxide or zirconium oxide material during elevated temperature processing; making capacitor, ferroelectric field effect transistor, and microelectronic device; and for sealing porosity in substrate (all claimed).    ADVANTAGE - The silylene compounds are usefully employed to form high purity, conformal silicon-containing films of SiO2, Si3N4, silicon carbide (SiC) and doped silicates in the manufacture of microelectronic device products. Improvements and new chemistries for vapor deposition of silicon-containing films for manufacturing microelectronic devices are provided.    DETAILED DESCRIPTION - Silicon precursor composition comprises a silylene compound selected from silylene compounds of formula I.    R and R1=independently selected from organo substituents; amidinate silylenes; and bis(amidinate) silylenes.    INDEPENDENT CLAIMS are included for:    (1) a method of forming a silicon-containing film on a substrate, involving volatilizing the silicon precursor composition to produce corresponding precursor vapor, and contacting the precursor vapor with the substrate under vapor deposition conditions to form the silicon-containing film on the substrate;    (2) a microelectronic device comprising the silicon-containing film deposited by the method;    (3) a silicon-containing film deposited by the method;    (4) a method of maintaining amorphous character of an amorphous hafnium oxide or zirconium oxide material during elevated temperature processing, involving incorporating silicon in the amorphous hafnium oxide or zirconium oxide material from the silicon precursor composition;    (5) a method of making a capacitor, involving forming a bottom electrode; depositing on the bottom electrode hafnium-silicate (HfSiO) amorphous film by a vapor deposition process, using a silicon precursor composition, an organohafnium precursor, and an oxic medium in the vapor deposition process; and forming a top electrode on the HfSiO amorphous film;    (6) a method of making a ferroelectric field effect transistor, involving forming a base comprising source and drain regions; depositing on the base, in contact with the source and drain regions, an oxide layer; forming on the oxide layer a HfSiO material by a vapor deposition process, using a silicon precursor composition, an organohafnium precursor, and an oxic medium in the vapor deposition process; depositing a metal-containing layer on the HfSiO material; and annealing the HfSiO material to form ferroelectric HfSiO material; and    (7) a method of sealing porosity in a substrate comprising porous silicon oxide, involving volatilizing silicon precursor composition to produce corresponding precursor vapor, and contacting the precursor vapor with the substrate under vapor deposition conditions including: (i) temperature in a range of from 50 degrees C to 200 degrees C; and (ii) presence of oxidant, to deposit silicon oxide in the porosity of the substrate for sealing.