A microelectromechanical (MEMS) device is provided that includes a microelectronic substrate and a thermally actuated microactuator and associated components disposed on the substrate and formed as a unitary structure from a single crystalline material, wherein (the associated components are actuated by the microactuator upon thermal actuation thereof. For example, the MEMS device may be a valve. As such the valve may include at least one valve plate that is controllably brought, into engagement with al least one valve opening in the microelectronic substrate by selective actuation of the microactuator. While the MEMS device can include various microactuators, the microactuator advantageously includes a pair of spaced apart supports disposed on the substrate and at least one arched beam extending therebetween. By heating the at least one arched beam of the microactuator, the arched beams will further arch such that the microactuator moves between a closed position in which the valve plate sealingly engages the valve opening and an open position in which the valve plate is at least partly disengaged from and does not seal the valve opening. The microactuator may further include metallization traces on distal portions of the arched beams to constrain the thermally actuated regions of arched beams to medial portions thereof. The valve may also include a latch for maintaining the valve plate in a desired position without requiring continuous energy input to the microactuator. An advantageous method for fabricating a MEMS valve having unitary structure single crystalline components is also provided.