Embodiments of the present invention are directed to forming an airgap-based vertical field effect transistor (VFET) without structural collapse. A dielectric collar anchors the structure while forming the airgaps. In a non-limiting embodiment of the invention, a vertical transistor is formed over a substrate. The vertical transistor can include a fin, a top spacer, a top source/drain (S/D) on the fin, and a contact on the top S/D. A dielectric layer is recessed below a top surface of the top spacer and a dielectric collar is formed on the recessed surface of the dielectric layer. Portions of the dielectric layer are removed to form a first cavity and a second cavity. A first airgap is formed in the first cavity and a second airgap is formed in the second cavity. The dielectric collar anchors the top S/D to the top spacer while forming the first airgap and the second airgap.