We fabricated Si single-electron transistors (SETs) having double SiO2 barriers and a polycrystalline Si (poly-Si) dot. The fabrication method of this device is completely compatible with the complementary metal–oxide–semiconductor technology, and the position of the poly-Si dot is self-aligned between the source and drain regions. The device exhibits drain current (Id) oscillation against gate voltage. From the dot size dependence of the electrical characteristics, the Id oscillation is considered to be due to the Coulomb blockade effect caused by poly-Si grains in the poly-Si dot. The self-alignment of the poly-Si dot in the fabrication process also means that the SET is promising for practical use.