A method for making an organic field effect transistor of a bottom gate/bottom contact type or a bottom gate/top contact type is provided. The method comprises (a) forming a gate electrode 12 on a support and forming a gate insulating layer 13 on the support 10 and the gate electrode 12, and (b) forming, on the gate insulating layer 13, source/drain electrodes 14 and an organic semiconductor region 15 made of an organic semiconductor material and constituting a channel forming region 16. The gate insulating layer 12 is formed by applying a solution of a mixture of an insulating polymer material and a surface treating agent onto the support 10 and the gate electrode 12 and drying. The organic field effect transistors are also provided.