Quantum phase transitions in two layers of ultrasmall Josephson juncti
ons, coupled capacitively with each other, are investigated. As the in
ter-layer capacitance is increased, the system at zero temperature is
found to exhibit an insulator-to-superconductor transition. It is show
n that, unlike in the case for one-dimensional arrays with a similar c
oupling configuration, the transition cannot be accounted for exclusiv
ely by particle-hole pairs.