A capacitive micro-machined ultrasonic transducer (CMUT) array includes an improved elementary aperture for imaging operations. The transducer can be of a linear, curved linear, annular, matrix or even single surface configuration. The elementary apertures thereof are formed by a specific arrangement of capacitive micromachined membranes (CMM) so as to exhibit ideal acoustical and electrical behavior when operated with imaging systems. The CMM arrangements can be either conventional where the element transducers of the array are uniformly shaped by predefined CMMs in a manner such as to exhibit acoustic behavior similar to a piezoelectric transducer, or can be more sophisticated, wherein each element transducer is formed by a specific combination of different CMMs (i.e., of a different size and/or shape) so as to provide the transducer with built-in acoustic apodization that can be implemented in the azimuth and/or elevation dimension of the device.