Micromachining techniques have been developed and applied in fabricating high frequency piezoelectric composite 2-dimensional ultrasound array transducers. The array has 256 elements with the size of 105 mu m by 105 mu m. The kerf between elements is 5 mu m. The center frequency is 52 MHz with the -6 dB bandwidth of 58%. As many as 98% elements are working. The pulse-echo responses have been measured with the testing system.