Feasibility studies and examples of integration of Si-based miniaturized biosensors are discussed. We investigated three main issues: (i) device surface functionalization, (ii) biological molecule functionality after immobilization and (iii) biosensor working principle using electrical transduction mechanism in order to fabricate electrolyte-insulator-semiconductor (EIS) and, in the near future, ion-sensitive field-effect transistor (ISFET) biosensors.We compared a well established method for the immobilization of bio-molecules on Si oxide with a new immobilization protocol, both providing a covalent bonding on SiO2 surfaces of proteins (metallothioneines) enzymes (glucose oxidase, horse radish peroxidase), or DNA strands. The process steps were characterized by means of contact angle, XPS and TEM measurements. The compatibility with Ultra Large Scale Integration (ULSI) technology of the two protocols was also …