Surface plasmon resonance (SPR) can be used to detect the change in reflective index on a metal surface. In this report, we propose detection of the SPR can easily be applied to estimate the thickness of the amorphous carbon (a-C: H) films. To detect changes in film thickness using SPR, devices with an a-C:H/Au structure were fabricated. The a-C:H films were deposited by electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) and sputtering, and the obtained film densities were 1.4 and 1.6 g/cm(3), respectively. By the deposition of an 11-nm thick a-C:H film on a Au layer by sputtering, the SPR angle changed from 44.90 degrees to 47.05 degrees. For a-C:H deposited by ECR-CVD, the SPR angle was shifted from 44.24 degrees for Au without the a-C:H layer to 58.44 degrees after deposition of 45 nm thick a-C:H film. In both systems of the SPR angle increased with increasing the film thickness. The rate at which the SPR angle shifted depended on the a-C:H film density. These results show that the thickness of an a-C:H filmcan be determined by the SPR angle shift on an a-C:H layer using a-C:H/Au device with an a-C:H film of the same density. (C) 2009 Elsevier B.V. All rights reserved.