Sensing field effect transistor devices and method of their manufacture

A sensing device includes a sensor die having a sensing region formed at a first surface of the sensor die. The sensing device further includes an encapsulant covering the sensing die, the encapsulant having a cavity formed therein, wherein the cavity exposes the sensing region. A sensitive membrane material is deposited within the cavity over the sensing region. A method of manufacturing sensing devices entails mounting a plurality of sensing dies to a carrier, encapsulating the dies in an encapsulant, forming cavities in the encapsulant, the cavities exposing a sensing region of each sensor die, and depositing the sensitive membrane material within each of the cavities. The encapsulating and forming operations can be performed simultaneously using a film-assisted molding (FAM) process, and the depositing operation is performed following FAM at an ambient temperature that is lower than the temperature needed to perform FAM.