An implantable electrical stimulation device includes an electrically conductive electrode structure configured for coupling with a pulse generator device and transmitting an electrical signal configured to generate a desirable electric field around a target tissue. The electrode structure includes a porous substrate constructed of a bio-compatible and bio-survivable material having a structure that mimics extracellular matrix embedding. The porous substrate supports an electrically conductive electrode element. The implantable device may further include a pulse generator also embedded, enmeshed, and supported within the porous substrate.