Abstract: A semiconductor device comprises a substrate (11) having an insulating layer (12) formed on a surface thereof, and a silicon layer (13) located on a surface of the insulating layer. A trench (14) extends from a surface of the silicon layer (13) through the insulating layer (12) and into the substrate (11). An insulating liner (14a) is located on the side walls and the base of the trench (14), and an in-fill (14b) of thermally-conductive material is formed within the insulating liner. The insulating liner (14a), the in-fill material (14b) and the distance over which the trench 14) extends into the substrate (11) are such as to promote flow of heat from the silicon layer (13) to the substrate.

Abstract: A method of forming an electrical isolation trench in a silicon-on-insulator (SOI) structure. The method comprises forming a first oxide layer on top of the upper silicon layer of the SOI structure, forming a polysilicon layer on top of said oxide layer, forming a second oxide layer on top of said polysilicon layer, patterning the first oxide layer, polysilicon layer, and second oxide layer to provide an etch mask, etching the upper silicon layer of the SOI structure to form said trench, and removing said second oxide layer and said polysilicon layer.