Langasite single crystals show piezoelectrically excited bulk acoustic waves up to 1470 °C and are, therefore, used to prepare high‐temperature functional components such as membranes, cantilevers and field emission tips. The underlying concept includes monolithic structures to avoid thermal stress at elevated temperatures. In order to control the preparation processes, wet chemical etch rates, the transport of dopants and their impact on the materials properties of langasite are determined. Heavily Sr‐doped langasite shows a strong increase in conductivity which is used to realize monolithic electrodes by local doping. Further, the stability of small langasite structures is confirmed up to 1350 °C. Biconvex membranes could be operated in the fundamental and 3rd resonance mode up to 700 °C. The fundamental modes of those 16.3 MHz resonators show quality factors of 500 at the above‐mentioned temperature. Further, field emitter tips of 27 nm in radius are prepared and demonstrated to be operational up to at least 600 °C. The mechanical displacement and the electrical response of vibrating cantilevers is characterized simultaneously and found to be consistent. Finally, the feasibility of sensor film coated membrane arrays to distinguish between CO and H2 at 600 °C is demonstrated.

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Piezoelectrically actuated plano‐convex thickness shear mode (TSM) resonators in lanthanum gallium silicate (langasite, LGS, La3Ga5SiO14) were fabricated. For the fabrication of the devices different micromachining technologies were investigated. Finally, a wet etching process and a dry etching process were developed and furthermore graytone‐lithography in combination with photoresist melting has been applied for the final device fabrication. The plano‐convex shape of the resonators is necessary to improve the Q‐factor of the devices. Simulations have been run to show the influence of the spherically contoured surface. The resulting Q‐factor was higher than for simple planar resonators, reaching values of about 25 000. Furthermore, the conductance spectra were significantly improved. The special characteristics of langasite allow working temperatures of up to 1450 °C. At 800 °C Q‐factors of 1700 could be achieved.

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