Buffer layer to prevent etching by photoresist developer

A method of fabricating a quantum circuit device, the method comprising:

• providing a device having a first layer and a second layer in contact with a surface of the first layer, wherein the second layer comprises a first superconductor material that exhibits superconducting properties at or below a corresponding superconducting critical temperature;
• forming a buffer material on a surface of the second layer to form an etch buffer layer, wherein an etch rate selectivity of the buffer material relative to the second layer upon exposure to a photoresist developer is such that the underlying second layer is not etched during exposure of the buffer layer to the photoresist developer;
• depositing and removing a selected portion of a resist layer to uncover a first portion of the etch buffer layer, wherein removing the selected portion of the resist layer comprises applying the photoresist developer to the selected portion of the resist layer;
• removing the uncovered first portion of the etch buffer layer to uncover a first portion of the second layer;
• and
• forming a dielectric material or a second superconductor material, which exhibits superconducting properties at or below a corresponding superconducting temperature, on the uncovered first portion of the second layer, wherein the second layer and the dielectric material or the second layer and the second superconductor material form part of the quantum circuit device, and wherein the quantum circuit device comprises a parallel plate capacitor or a microstrip resonator.