Implementations described herein generally relate to processes for the fabrication of semiconductor devices in which a blocking layer of molecules is used to achieve selective epitaxial deposition. In one implementation, a method of processing a mixed-surface substrate comprising an exposed dielectric material and an exposed silicon-based material is provided. The method comprises depositing a blocking layer on the exposed dielectric material and epitaxially and selectively depositing a silicon-containing material layer on the exposed silicon-based material at a temperature of 400 degrees Celsius or greater. The method further involves removing the blocking layer from the dielectric material.