A method of fabrication of an integrated circuit is provided, including: providing a substrate including a first active layer and a first metallic level of interconnection arranged on top of the active layer and including first lines of interconnection separated by a first filling of sacrificial material; forming a superposition of an insulator layer and second lines of interconnection; providing access to the first filling through the insulator layer; filling the provided access with a second filling of sacrificial material; forming a second active layer on top of the second metallic level of interconnection; providing access to the second filling through the second active layer; and removing the first and the second fillings by a chemical etching through the provided access to the second filling.