Atomic　layer　deposition　(ALD)　and　rapid　atomic　layer　deposition　(RALD)　have　emerged　as　useful　techniques　for　depositing　highly　conformal　and　uniform　thin　films　for　advanced　semiconductor　devices.　The　performance　of　the　ALD　or　RALD　process　depends　on　the　design　of　precursor　molecules.　In　this　work,　the　aminosilane　precursor　molecules　(bis(tertbutylamino)silane　(BTBAS),　bis(diethylamino)silane　(BDEAS),　and　tris(dimethylamino)silane　(TDMAS))　in　ALD　and　two　silanol　precursors　(tris(tert-butoxy)silanol　(TBS)　and　tetra(tert-butoxy)silane　[(tBuO)4Si])　in　RALD　were　investigated　using　first-principles　based　on　density　functional　theory.　The　energy　diagrams　of　the　growth　process　on　the　hydroxylated　SiO2(0　0　1)　surface　were　calculated　for　each　precursor.　Furthermore,　the　rate-determining　step　was　confirmed,　and　the　precursors　were　compared　in　terms　of　thermochemical　energies　and　activation　barriers.　BTBAS　showed　the　lowest　energy　barrier　in　the　rate-determining　step　among　all　precursors,　which　suggested　that　the　rapid　rate　of　RALD　might　be　due　to　the　addition　of　trimethylaluminum　catalyst.　Moreover,　during　the　decomposition　process　of　ALD　and　RALD,　the　bond　length　at　the　transition　state　demonstrated　a　correlation　with　the　reaction　activation　energies,　which　provided　a　new　perspective　for　studying　these　processes.　This　work　helps　clarify　the　reaction　processes,　facilitating　the　design　and　preparation　of　more　efficient　precursors.