Bypass/Decoupling Capacitor Characteristics
A series resonance occurs with an IC external local bypass capacitor, between it's capacitance and inherent
inductance. So often bypassing operates in the capacitors inductive region. It's therefore advantageous to minimise the
associated inductance using multiple capacitors (generally of the same value) in order to provide a low impedance.
Capacitors are also available with increased width for reduced inductance see:
Low-inductance MLCCs for ligh-speed digital systems. Phycomp-Yageo an08432. (PDF)
When considering capacitors fabricated with Y5V high dielectric material, be aware that capacitance varies significantly with temperature.
Typical cap. characteristics vs. temp. with X7R, Z5U, Y5V. (PDF)
Also note that with ceramic capacitors, capacitance changes (reduces) with DC voltage applied.
Capacitance change with voltage applied 0201 X5R 100nF. (PDF)