A touch sensor mechanism for a touch display device, includes a cover lens made by a transparent material having a dielectric constant greater than 4.5 and a compression strength greater than 700 MPa for generating a finger's touching capacitance (CF) while a user's finger of a user touch thereon; and a sensor device module including a plurality of sensor devices having a sensor parasitic capacitance (CP). The cover lens and the sensor device module are disposed in the touch display device in such a manner that a ratio of a standard deviation value (σU) of the finger's touching capacitance (CF) of the cover lens to the sensor parasitic capacitance (CP) of the sensor device module is a signal-to-noise ratio (SNR). The SNR is adjusted along with the finger's touching capacitance (CF) by reducing the thickness of the cover lens.