Metal‐insulator‐semiconductor field effect transistors have been fabricated using laser ablation to deposit YBaCuO thin films onto SrTiO3, MgO, LaAlO3, and LaGaO3substrates. The substrates were used as gate insulators. The conductivity of two films on SrTiO3could be modulated, while for other samples the conductivity was independent of the gate voltage. The field‐effect mobility was extracted and found to be of magnitude comparable to the mobility of metallic YBa2Cu3O7.