Conformal and continuous silicon containing films produced by Atomic Layer Deposition (ALD) are enabling novel processing schemes and integrated device structures. The increasing drive towards lower temperature processing requires new precursors with even higher reactivity. A systematic method for identification of high performance precursors is thus very desirable, and needs to incorporate fundamental understanding of precursor chemistry, surface reactions; and relationships between precursor structure and deposited films. The overall approach accordingly relies on integrating molecular and surface reaction modeling, the ability to synthesize stable precursors with reactive groups, in-situ surface studies, and thin film deposition testing. To illustrate this approach, two case-studies will be discussed in this presentation: silicon oxide and silicon nitride ALD. In both cases, a representative monoaminosilane (R1R2N)SiH3 called di-sec-butylaminosilane (DSBAS) will be studied. The impact of changing the precursor structure will also be discussed.