Protein and gene detection have been growing importance in medical diagnostics. Field effect transistor (Phi`) - type biosensors have many advantages such as miniaturization, standardization, andmass-production. In this work, we have fabricated metal-oxide-semiconductor (MOS) FET that operates as molecular recognitions based electronic sensor. Measurements were taken with the devices under phosphate buffered saline solution. The drain current (I_(D)) was decreased after forming self-assembled mono-layers (SAMs) used to capture the protein, which resulted from the negative charges of SAMs, and increased after forming protein by 11,5% at V_(G)= 0 V due to the positive charges of protein.