Organic TFTs with p-type pentacene and n-type F16CuPc were fabricated on both Si and plastic substrates. Maximum p-type mobility of 0.8 cm(2)/Vs and 0.12 cm(2)/Vs were achieved for Si and plastic substrates, respectively. JSS-362 was used as a gate dielectrics for plastic substrate. To decrease the contact resistance between metal electrodes and organic semiconductors, self-assembled monolayers were formed. Charge carrier mobilities of the device with both pentacene and F16CuPc were increased after SAMs treatments on metal contacts.