A method of fabricating a thickness shear mode (TSM) gas and organic vapor sensor having a visco-elastic polymer coating and a fundamental frequency greater than 20 MHz. The method begins by providing a piezoelectric crystal and milling a central region of the crystal. Milling the crystal creates a central oscillating region of reduced thickness surrounded by a thicker outer region. Two electrodes are then deposited in the oscillating region of the crystal—one on each side of the crystal. The oscillating region on both sides of the crystal and the electrodes are then coated with a polymer coating.