NOVELTY - The device has a top thin film barrier material (180) for preventing oxygen, water, nitrogen and carbon dioxide species from diffusing into first and second electrochemical cells and covering the first and second electrochemical cells. An exposed region is formed within a portion of the thin film barrier material to expose contact regions of current collectors (120, 160). Intermediary thin film barrier material (170) prevents migration of ionic species from the first electrochemical cell to the second electrochemical cell or the second electrochemical cell to the first electrochemical cell.    USE - Thin film solid state battery device for use in a portable electronic device e.g. cell phone, personal digital assistant, music player and video camera, a power tool and a power supply used in a vehicle e.g. hybrid electric vehicle, plug-in hybrid electric vehicle and fully electric vehicle for military application and aerospace applications.    ADVANTAGE - The device has higher energy and power densities and longer cycle life. The top thin film barrier material is formed using material having inherently low permeability to oxygen and water, so that the barrier material can be free of defects that permit oxygen and water passing through the barrier material.    DETAILED DESCRIPTION - The ionic species comprises lithium ion. The intermediary thin film barrier material, a bottom thin film barrier material and the top thin film barrier material are made of a material selected from a group consisting of oxide of metal or metalloid, nitride of metal or metalloid, carbide of metal or metalloid and phosphate of metal. The device has a substrate selected from a group consisting of copper material, aluminum material and polymer material. An INDEPENDENT CLAIM is also included for a method for fabricating a solid state battery device.    DESCRIPTION OF DRAWING(S) - The drawing shows a side cross-sectional view of a thin film electrochemical cell.    Substrate (100)    Bottom barrier material (110)    Current collectors (120, 160)    Intermediary thin film barrier material (170)    Top thin film barrier material (180)