MEMS resonator

A method of fabricating a microelectromechanical system (MEMS) resonant structure, the method comprising:

• forming a silicon-on-insulator structure having an insulating material layer disposed between a first degenerately-doped silicon layer and a substrate layer;
• epitaxially growing an aluminum nitride material layer on the first degenerately-doped silicon layer;
• forming a second degenerately-doped silicon layer on the aluminum nitride material layer such that the aluminum nitride material layer is sandwiched between the first and second degenerately-doped silicon layers;
• and
• removing at least a portion of the insulating material layer from beneath the first degenerately-doped silicon layer;
• wherein the first degenerately-doped silicon layer is to serve as a first electrode for the MEMS resonant structure and the second degenerately-doped silicon layer is to serve as a second electrode for the MEMS resonant structure, each in absence of a metal electrode layer;
• and
• wherein the method further comprises forming the MEMS resonant structure such that the aluminum nitride material layer and one of the first or second degenerately-doped silicon layers, respectively, have reciprocal-polarity parabolic temperature coefficients of frequency.

A method of fabricating a microelectromechanical system (MEMS) resonant structure, the method comprising:

• forming a silicon-on-insulator structure having an insulating material layer disposed between a first degenerately-doped silicon layer and a substrate layer, the first degenerately-doped silicon layer comprising a first one of polysilicon and single-crystal silicon;
• epitaxially growing an aluminum nitride material layer on the first degenerately-doped silicon layer;
• forming a second degenerately-doped silicon layer on the aluminum nitride material layer such that the aluminum nitride material layer is sandwiched between the first and second degenerately-doped silicon layers, the second degenerately-doped silicon layer comprising a second one of polysilicon and single-crystal silicon;
• and
• removing at least a portion of the insulating material layer from beneath the first degenerately-doped silicon layer;
• wherein the first degenerately-doped silicon layer is to serve as a first electrode for the MEMS resonant structure and the second degenerately-doped silicon layer is to serve as a second electrode for the MEMS resonant structure, each in absence of a metal electrode layer;
• and
• wherein the method further comprises forming the MEMS resonant structure such that at least one of the first degenerately-doped silicon layer and the second degenerately-doped silicon layer comprises single-crystal silicon, and such that the single-crystal silicon has a predetermined angular deviation between a crystallographic orientation of the single-crystal silicon and a resonance mode orientation of the MEMS resonant structure.