  Efficient design and performance of electrically actuated MEMS devices
necessitate accurate estimation of electrostatic forces on the MEMS structures.
This in turn requires thorough study of the capacitance of the structures and
finally the charge density distribution on the various surfaces of a device. In
this work, nearly exact BEM solutions have been provided in order to estimate
these properties of a parallel narrow beam structure found in MEMS devices. The
effect of three-dimensionality, which is an important aspect for these
structures, and associated fringe fields have been studied in detail. A
reasonably large parameter space has been covered in order to follow the
variation of capacitance with various geometric factors. The present results
have been compared with those obtained using empirical parametrized expressions
keeping in view the requirement of the speed of computation. The limitations of
the empirical expressions have been pointed out and possible approaches of
their improvement have been discussed.
