We studied the enzyme glucose oxidase (GOx) immobilization on silicon oxide surfaces. In particular, we optimized the immobilization protocol and verified that it fulfills both requirements of enzyme preservation (measured by enzymatic activity) and VLSI compatibility. The immobilization consists of four steps: oxide activation, silanization, linker molecule deposition and GOx immobilization. It is crucial to form an uniform linker layer on the sample surface in order to maximize the sites available for enzyme bonding and achieving the best enzyme deposition. In this study, utilizing glutaraldehyde as bifunctional reagent, we monitored its uniformity on the surface through X-ray Photoelectron Spectroscopy (XPS). Once optimized, the same protocol was used to anchor the enzyme in a porous silicon dioxide matrix. Gold labeled GOx molecules were monitored by electron diffraction X-ray (EDX) measurements coupled with scanning electron microscopy (SEM). The enzymatic activity was also monitored to confirm the goodness of the proposed immobilization method. Finally, the electrical characterization of MOS capacitors, showing a shift of about 1 V in the flat band voltage, demonstrated the possibility to use this approach for electrical detection.