Method for creating a crystalline layer from a crystalline substrate made of a first material; the method comprising the following steps: - depositing a masking layer on the substrate, the masking layer being formed by a stack of layers (201, 202), the materials of which differ from one layer to the other and are configured so as to be removed selectively with respect to each other, the masking layer comprising a first layer forming a stop layer above which there is at least a second layer, - forming, by etching of the masking layer, at least one trench in the masking layer, the trench forming an access to the substrate, the formation of the trench being carried out so that the trench has a depth at least equal to a value Hc such that Hc= K.S.tan(θ) where K is at least greater than 0.7, S is the width of the trench and θ is the angle formed by a plane in which the substrate mainly extends and dislocations of the material of the buffer layer located in the trench, - forming a crystalline buffer layer located at least partly in the trench of the masking layer, extending from the substrate and forming a protrusion beyond the first layer of the masking layer so that an upper part of the lateral sides of said buffer layer is left exposed, the formation step comprising a growth of the buffer layer from the crystalline substrate so as to give the buffer layer a crystalline structure by using the crystalline structure of the crystalline substrate, the formation of the buffer layer comprising, after the growth of the buffer layer from the substrate, a step of removing a part of the masking layer so as to expose said upper part of the lateral sides of the buffer layer, the step of removing a part of the masking layer being carried out by etching of the second layer with stoppage on the first layer, - forming a crystalline epitaxial layer made of a second material, different from the material of the buffer layer, by growth from said upper part of the lateral sides of the buffer layer left exposed, the material of the buffer layer and the material of the epitaxial layer having a difference in mesh parameter of less than 2%, the formation of the buffer layer being carried out so as to leave exposed an upper face of the buffer layer in addition to said upper part of the lateral sides of the buffer layer, before the formation of the epitaxial layer, forming a protective layer on said upper face of the buffer layer so as to leave exposed only said upper part of the lateral sides of the buffer layer left exposed, and, after the formation of the epitaxial layer on either side of the buffer layer, removing the buffer layer selectively with respect to the epitaxial layer so as to leave in place a first channel and a second channel formed by the epitaxial layer; said first and second channel (525, 575) being electrically insulated and each forming a transistor channel preferably of the FinFET type. - depositing a masking layer on the substrate, the masking layer being formed by a stack of layers (201, 202), the materials of which differ from one layer to the other and are configured so as to be removed selectively with respect to each other, the masking layer comprising a first layer forming a stop layer above which there is at least a second layer, - forming, by etching of the masking layer, at least one trench in the masking layer, the trench forming an access to the substrate, the formation of the trench being carried out so that the trench has a depth at least equal to a value Hc such that Hc= K.S.tan(θ) where K is at least greater than 0.7, S is the width of the trench and θ is the angle formed by a plane in which the substrate mainly extends and dislocations of the material of the buffer layer located in the trench, - forming a crystalline buffer layer located at least partly in the trench of the masking layer, extending from the substrate and forming a protrusion beyond the first layer of the masking layer so that an upper part of the lateral sides of said buffer layer is left exposed, the formation step comprising a growth of the buffer layer from the crystalline substrate so as to give the buffer layer a crystalline structure by using the crystalline structure of the crystalline substrate, the formation of the buffer layer comprising, after the growth of the buffer layer from the substrate, a step of removing a part of the masking layer so as to expose said upper part of the lateral sides of the buffer layer, the step of removing a part of the masking layer being carried out by etching of the second layer with stoppage on the first layer, - forming a crystalline epitaxial layer made of a second material, different from the material of the buffer layer, by growth from said upper part of the lateral sides of the buffer layer left exposed, the material of the buffer layer and the material of the epitaxial layer having a difference in mesh parameter of less than 2%, the formation of the buffer layer being carried out so as to leave exposed an upper face of the buffer layer in addition to said upper part of the lateral sides of the buffer layer, before the formation of the epitaxial layer, forming a protective layer on said upper face of the buffer layer so as to leave exposed only said upper part of the lateral sides of the buffer layer left exposed, and, after the formation of the epitaxial layer on either side of the buffer layer, removing the buffer layer selectively with respect to the epitaxial layer so as to leave in place a first channel and a second channel formed by the epitaxial layer;