Selective atomic layer deposition for gapfill using sacrificial underlayer

Methods and apparatuses for depositing films in high aspect ratio features and trenches on substrates using atomic layer deposition and deposition of a sacrificial layer during atomic layer deposition are provided. Sacrificial layers are materials deposited at or near the top of features and trenches prior to exposing the substrate to a deposition precursor such that adsorbed precursor on the sacrificial layer is removed in an etching operation for etching the sacrificial layer prior to exposing the substrate to a second reactant and a plasma to form a film.