A method of manufacturing a resonant transducer having a vibration beam, the method comprising: (a) providing an SOI substrate comprising: a first silicon layer; a silicon oxide layer on the first silicon layer; and a second silicon layer on the silicon oxide layer; (b) forming a first gap and second gap through the second silicon layer by etching the second silicon layer using the silicon oxide layer as an etching stop layer; (c) forming an impurity diffusion source layer (102, 401) on the second silicon layer, wherein the impurity diffusion source layer is configured to diffuse impurity into the second silicon layer; (d) forming an impurity diffused layer (103, 402) in a surface portion of the second silicon layer by diffusing the impurity from the impurity diffusion source layer through heat treatment for the SOI substrate in order to increase tensile strain of the vibration beam; (e) removing the impurity diffusion source layer through etching; and (f) removing at least a portion of the silicon oxide layer through etching such that an air gap is formed between the first silicon layer and a region of the second silicon layer surrounded by the first and second gaps, wherein the region of the second silicon layer surrounded by the first and second gaps serves as the vibration beam, wherein the step (c) is performed after the step (b), and wherein the step (c) comprises: forming the impurity diffusion source layer on an upper surface of the second silicon layer, on an inner wall surface of the second silicon layer that is in contact with the first and second gaps, and on a portion of the silicon oxide layer which is exposed through the first and second gaps, wherein the step (d) comprises: forming the impurity diffused layer in the surface portion of the second silicon layer by diffusing the impurity into both the upper surface and the inner wall surface of the second silicon layer through the heat treatment for the SOI substrate. (a) providing an SOI substrate comprising: a first silicon layer; a silicon oxide layer on the first silicon layer; and a second silicon layer on the silicon oxide layer; (b) forming a first gap and second gap through the second silicon layer by etching the second silicon layer using the silicon oxide layer as an etching stop layer; (c) forming an impurity diffusion source layer (102, 401) on the second silicon layer, wherein the impurity diffusion source layer is configured to diffuse impurity into the second silicon layer; (d) forming an impurity diffused layer (103, 402) in a surface portion of the second silicon layer by diffusing the impurity from the impurity diffusion source layer through heat treatment for the SOI substrate in order to increase tensile strain of the vibration beam; (e) removing the impurity diffusion source layer through etching; and (f) removing at least a portion of the silicon oxide layer through etching such that an air gap is formed between the first silicon layer and a region of the second silicon layer surrounded by the first and second gaps, wherein the region of the second silicon layer surrounded by the first and second gaps serves as the vibration beam, wherein the step (c) is performed after the step (b), and wherein the step (c) comprises: forming the impurity diffusion source layer on an upper surface of the second silicon layer, on an inner wall surface of the second silicon layer that is in contact with the first and second gaps, and on a portion of the silicon oxide layer which is exposed through the first and second gaps, wherein the step (d) comprises: forming the impurity diffused layer in the surface portion of the second silicon layer by diffusing the impurity into both the upper surface and the inner wall surface of the second silicon layer through the heat treatment for the SOI substrate. forming the impurity diffusion source layer on an upper surface of the second silicon layer, on an inner wall surface of the second silicon layer that is in contact with the first and second gaps, and on a portion of the silicon oxide layer which is exposed through the first and second gaps, wherein the step (d) comprises: forming the impurity diffused layer in the surface portion of the second silicon layer by diffusing the impurity into both the upper surface and the inner wall surface of the second silicon layer through the heat treatment for the SOI substrate. forming the impurity diffused layer in the surface portion of the second silicon layer by diffusing the impurity into both the upper surface and the inner wall surface of the second silicon layer through the heat treatment for the SOI substrate.