Now 0603 is available in a Tantalum Capacitor

As the world's smallest surface mount tantalum capacitor, TACmicrochip is
a major breakthrough in miniaturization without a reduction in performance. It gives you the highest bulk energy storage in an 0603 case size, enhanced high frequency operation through unique ESR performance and temperature and voltage stability.

TACmicrochip is also available in 0805 size.