MEMS devices and processes

A MEMS transducer comprising a flexible membrane 405 with a membrane electrode 400 provided thereon. In the electrode layer there are a plurality of large primary openings (holes) 410 and in-between the primary openings there are smaller secondary openings 420. The primary and secondary openings mitigate the effects of reflow drift. The sections of the electrode between primary openings comprises an elongate beam having a longitudinal axis; the secondary openings are defined by a similar shape along this longitudinal axis. The secondary openings may be generally rectangular, oval or elliptical shape and the primary openings may be hexagonal, circular, square or rectangular. The MEMS transducer may comprise a back-plate electrode with a plurality of holes overlying the primary openings 412, 414 and the secondary openings are under the backplate electrode. The primary openings' perimeter, area, shape and size may correspond to the backplate electrode holes. Alternatively the primary openings may be smaller than the backplate holes. The primary openings may define a lattice structure with a plurality of secondary openings at regular intervals around the perimeter of each primary opening (Fig. 9). The MEMS transducer may be a capacitive microphone.