# Semiconductors/insulators: Why is the fermi energy between the valence and conduction band?

Ive asking myself a question on the fermi-energy. The fermi-energy is defined as the maximum energy which an electron, following the Pauli-rule, can have at T=0. In semiconductors and insulators the valence band is full while the conduction band is empty (at T=0). Thus the maximum energy is the upper edge of the valence band. Then why is the fermi-energy not this upper edge of the valence band and instead in the middle of valence and conduction band?

Thank you very much!