The general objective of this presentation is to demonstrate the great potential of InP-membrane photonic devices, with a special emphasis on applications for Optical Communications. Various classes of devices will be presented, which are based on MOEMS (Micro-Opto-Electro-Mechanical) structures, or 2 dimensional (2D)photonic crystals (PC) or a combination of both, according to a '2.5-dimensional' approach, which should broaden considerably the combinations of functionality beyond those presently contemplated with the two first classes. For the MOEMS devices, the basic building block consists in a multi-air-gap/suspended-membrane structure, which can be micro-machined using multi-layered III-V semiconductor based heterostructures : tunable filters will be presented for illustration. For PC devices, the basic building block consists in an InP (and related material) membrane including a 2D PC formed by a lattice of holes : the membrane is either suspended in air or bonded onto low index material, e.g. silica on silicon substrate, in the prospect of heterogeneous integration with silicon based microelectronics. Examples of devices will be presented, specifically micro-lasers based on 2D PC micro-cavities as well as on 2D in plane Bloch modes (2D Distributed-Feed-Back micro-laser). For the '2.5-dimensional' photonic structures, it will be shown that the multi-layer membrane approach, where individual layers or combinations of layers may be structured across to form a 2D PC, is naturally suitable for this purpose. Examples of devices will be presented (2D PC surface emitting micro-sources, switching devices combining vertical MOEMS multi-layer membrane structures and 2D PC).