SWRA640 Application note

4.5 Decoupling Capacitors

General rules for decoupling capacitors:

Ensure decoupling capacitors are on same layer as the active component for best results.
Route power into the decoupling capacitor and then into the active component.
Each decoupling capacitor should have a separate via to ground to minimize noise coupling (see Figure 4-5).
The decoupling capacitor should be placed close to the pin it is supposed decouple (see Figure 3-2).
The ground current return path between decoupling capacitor and chip should be short and direct (low impedance). For details, see Section 4.7.

Figure 4-5 Decoupling Capacitors and VIA to Ground

The right side of Figure 4-5 that uses separate vias to ground has less noise coupling.