Patent ID: 7777307

Claim:
A high-frequency signal transmission circuit device comprising: a semiconductor substrate having a recess on a surface thereof, the recess having first and second side surfaces, the first and second side surfaces being spaced apart; an etching resistant stopper material having at least first and second portions, the first portion formed on the first side surface and the second portion formed on the second side surface, wherein the recess is formed by an etching process that removes a portion of the semiconductor substrate directly between the first and second portions of the etching resistant stopper material, and wherein the etching resistant stopper material is configured to protect the first and second side surfaces from the etching process; and a high-frequency signal transmission line provided on the semiconductor substrate, the signal transmission line having a first portion extending over the recess and a second portion not extending over the recess, the first portion having a first characteristic impedance and the second portion having a second characteristic impedance, wherein the first characteristic impedance is dependent upon a depth of the recess and wherein the depth of the recess is such that the first characteristic impedance and the second characteristic impedance are matched.