A support member for semiconductor device elements includes a conductive layer separated from the semiconductor elements by an insulative layer. A protective potential lower than any operating potential applied to the semiconductor device elements is applied to the conductive layer. The relatively negative potential on the conductive layer forms an electric field for gettering mobile ions from layers of the support member both above and below the conductive layer. Additionally, the conductive layer within the support member serves as a second plate in construction of capacitors and as a wiring layer for use with the semiconductor device elements. Also, due to the reflective properties of the conductive layer, it may function as a light shield or reflector in the construction of optic devices.