A proton detector device was fabricated by the conventional silicon process, including photolithography, oxidation, ion implantation, and metal electrode sputtering. The detection sensitivity of the PIN silicon detector was measured with varying the proton beam acceleration energy to the maximum value of 8 MeV. The detector device was aligned with the carbon collimator to expose the proton beam to the active area of the detector. The size of the collimator was 3 x 3 mm(2) with the square shape, which was the same shape as the detector active area. The flux density of the proton beam was fixed as 10 nA during the beam exposure. The reverse bias voltage of the device was 5 V. The reverse Current of the device Was Measured with a digital oscilloscope. The detection sensitivity for the proton energy of the diode showed the energy linearity of 10% until the proton energy of 5 MeV. The linear region may be expanded until 30 MeV when Cu attenuators were used with varying the Cu thickness. (c) 2005 Elsevier B.V. All rights reserved.