Techniques for co-tuning of inductance (L) and capacitance (C) in a VNCAP-based LC tank oscillator are provided. In one aspect, an LC tank oscillator includes: a capacitor including at least two metal layers, each metal layer having metal fingers that are interdigitated, wherein an orientation of the metal fingers alternates amongst the at least two metal layers; and an inductor on the capacitor. Inter-layer vias can be present interconnecting the at least two metal layers creating conductive loops between the metal fingers, wherein an arrangement of the inter-layer vias in an area between the at least two metal layers is configured to co-tune both inductance and capacitance in the LC tank oscillator. A method of operating an LC tank oscillator and a method of co-tuning inductance and capacitance in an LC tank oscillator are also provided.