A valve includes: a body including: a wall defining a process surface, a process void in the process surface adapted to communicate with fluid at process pressure, and at least two vent voids in the wall separate from the process void; an inlet port in fluid communication with the process void; and an outlet port in fluid communication with the vent void; a reference housing adapted to communicate with fluid at reference pressure; and a membrane constrained between the body and the reference housing with its process side substantially coplanar with the process surface. The process surface incorporates at least one groove therein which defines a flow path between the near vicinity of the process void and the near vicinity of the vent voids.