Crystal grain diffusion barrier structure for a semiconductor device

Claim 1

A contact structure for connecting a semiconductor portion of a semiconductor device to a metal electrode used in the semiconductor device, said contact structure preventing reaction between the semiconductor portion of a semiconductor device and the metal electrode, said contact structure comprising: a semiconductor layer forming the semiconductor portion of the semiconductor device, said semiconductor layer including a component element and having a top major surface; a metal electrode used in the semiconductor device for wiring, said metal electrode including a component element and having a bottom major surface; a first barrier layer of an electrically conductive material including at least one component element, said first barrier layer having an upper major surface and a lower major surface and provided on the top major surface of the semiconductor layer for preventing the component element of said semiconductor layer and the component element of said metal electrode from being transported therethrough, said first barrier layer having a microstructure wherein a plurality of grains of said electrically conductive material, each defined by a grain boundary, are assembled to each other; an interface region formed in the first barrier layer as a part of the first barrier layer along the upper major surface of the first barrier layer, said interface region having an upper major surface coincident to the upper major surface of the first barrier layer and consisting essentially of a material which contains all the component elements forming the material of said first barrier layer but substantially free from said component element forming said semiconductor layer, said interface region having a microstructure which is different from the microstructure of the first barrier layer; and a second barrier layer having a lower major surface and an upper major surface, said second barrier layer including a material substantially identical to that of the first barrier layer and having a microstructure including a plurality of grains of the material forming the second barrier layer each defined by a grain boundary, said second barrier layer provided on the upper major surface of the first barrier layer and under the lower major surface of the metal electrode so as to be sandwiched between the first barrier layer and the metal electrode, said second barrier layer provided with respect to the first barrier layer such that the grains in the second barrier layer are located generally in correspondence to the grain boundary in the first barrier layer, said microstructure of said interface region for preventing said component element of said semiconductor layer and said component element of said metal electrode from being transported across the interface region.