Pt thin film was deposited on alumina substrate by using DC sputter and the serpentine pattern was formed by photolithography to fabricate the resistance temperature detector (RTD). The Pt film was thermally treated and the surface structure of the film and its effect on the electrical resistance were studied. The sheet resistance of the film depends on the thickness and thermal treatment. The developing and etching conditions for serpentine patterning of the film were investigated and various RTD samples were prepared. All of the fabricated RTD's show a good linear variation of resistance with the temperature. The temperature coefficient of resistance (TCR) values of RTD's increased with decreasing film thickness, narrowing pattern line width, and increasing annealing temperature. The highest TCR value was obtained from RTD with 1 mm line width thermally treated at 700 ℃ and was 3.53x10(3) ppm/℃.