Abstract: A trench-gate semiconductor device configuration is provided which is suitable for incorporation in integrated circuits, together with methods for its manufacture. A self-aligned drain region (12a) is provided below the device trench (18). The manufacturing methods include etching an initial trench into a semiconductor body (8), and annealing so as to cause migration of material such that a shallower trench with a cavity (36) below it are formed. The drain region is then formed in the cavity.

Abstract: The present invention discloses a method of forming a local buried layer (32) in a silicon substrate (10), comprising forming a plurality of trenches (12, 22) in the substrate, including a first trench (22) having a width preventing sealing of the first trench in a silicon migration anneal step and at least one further trench (12) connected to the first trench; exposing the substrate (10) to said anneal step, thereby converting the at least one further trench (12) by means of silicon migration into at least one tunnel (16) accessible via the first trench (22); and forming the local buried layer (32) by filling the at least one tunnel (16) with a material (26, 28, 46) via the first trench (22). Preferably, the method is used to form a semiconductor device having a local buried layer (32) comprising a doped epitaxial silicon plug (26), said plug and the first trench (22) being filled with a material (28) having a higher conductivity than the doped epitaxial silicon (26).