Abstract: A single source predeposition is required to concurrently form a base diffusion profile and p.sup.+ profile. For a boron doped silicon semiconductor devices this can be accomplished by depositing a silicon nitride layer directly over a boron source glass layer. After opening windows to the underlying silicon, diffusion in a wet oxide atmosphere results in formation of a resulting oxide in the windows with expenditure of boron by diffusion into this oxide as well as diffusion into the underlying substrate at a reduced concentration. In adjacent areas masked by the silicon nitride the boron source diffuses unidirectionally into the substrate yielding a maximum dopant concentration.