  We report on fabrication and characterization of the organic field effect
transistors (OFETs) on the surface of single crystals of rubrene. The parylene
polymer film has been used as the gate insulator. At room temperature, these
OFETs exhibit the p-type conductivity with the field effect mobility up to 1
cm^2/Vs and the on/off ratio ~ 10^4. The temperature dependence of the mobility
is discussed.
