The invention relates to a structure for radiofrequency applications comprising: a monocrystalline substrate, a polycrystalline silicon layer directly on the monocrystalline substrate, and an active layer on the polycrystalline silicon layer intended to receive radiofrequency components. At least a first portion of the polycrystalline silicon layer extending from an interface of the polycrystalline silicon layer with the monocrystalline substrate layer includes carbon and/or nitrogen atoms located at the grain boundaries of the polycrystalline silicon layer at a concentration of between 2% and 20%. A process for manufacturing such a structure includes, during deposition of at least a first portion of such a polycrystalline silicon layer located at the interface with the monocrystalline substrate, depositing carbon and/or atoms in the at least a first portion.