A method of producing a semiconductor disk represented by a composition formula [(Bi.sub.0.5Na.sub.0.5).sub.x(Ba.sub.1-yR.sub.y).sub.1-x]TiO.sub.- 3, in which R is at least one element of La, Dy, Eu, Gd and Y and x and y each satisfy 0.ltoreq.x.ltoreq.0.14, and 0.002.ltoreq.y.ltoreq.0.02 includes carrying out a sintering in an inert gas atmosphere with an oxygen concentration of 9 ppm to 1% and wherein a treatment at an elevated temperature in an oxidizing atmosphere after the sintering is not carried out.