Formation of organosilane monolayers having various functional groups on silicon oxide surfaces for fabricating on-chip biosensing devices was investigated. Alkyl and perfluoro-alkyl functionalized monolayers were prepared by a chemical vapor deposition, and amino functionalized monolayers were formed by a liquid phase reaction. Each monolayer was confirmed to be closely packed and composed of single moiety species. A molecular patterning process using these organic monolayers was performed. The monolayer patterns were uniformly formed on the substrate by using ultraviolet light patterning and oxygen plasma ashing processes. The pH responsibility at the liquid/modified electrode interface was examined by using capacitor profiles of the structure of monolayer/silicon oxide/silicon. The amino modified surface showed good pH sensitivity of -44 mV/pH. This value was similar to that of the silicon nitride surface. On the other hand, the potential was not changed in any pH solutions in the case of the alkyl and perfluoro-alkyl monolayer-modified surface. It was demonstrated that the pH response of these surfaces was greatly affected by the variation of the functional group. Furthermore, by using the patterned monolayers, fabrication of a multichannel electrode for multiple detection of pH response was achieved.