A new phenacene-type molecule with five fused aromatic rings was synthesized: 2,7-didodecylphenanthro[2,1-b: 7,8-b'] dithiophene ((C12H25)(2)-i-PDT), with two terminal thiophene rings. Field-effect transistors (FETs) using thin films of this molecule were fabricated using various gate dielectrics, showing p-channel normally-off FET properties with field-effect mobilities (mu) greater than 1cm(2) V-1 s(-1). The highest mu value in the thin-film FETs fabricated in this study was 5.4 cm(2) V-1 s(-1), when a 150 nm-thick ZrO2 gate dielectric was used. This implies that (C12H25)(2)-i-PDT is very suitable for use in a transistor. Its good FET performance is fully discussed, based on electronic/topological properties and theoretical calculations.