Patent ID: 8381378

Claim:
A method of forming a micromechanical resonator operable in a bulk acoustic mode, comprising: forming a resonator body anchored to a substrate by at least a first anchor, said resonator body comprising a first material having a negative temperature coefficient of elasticity (TCE) and an array of spaced-apart trenches filled with a second material having a positive TCE, said array of spaced-apart trenches having a sufficient density in the resonator body to meet the following relationship: 1 ≦−R V (TCE I /TCE S )[( E I /E S )+(ρ I /ρ S ) 1/2 ( E I /E S ) −1/2 ]≦3, where R V =(V I /V S ); TCE S , E S , ρ S and V S represent the temperature coefficient of elasticity, Young's modulus, density and volume of the first material in the resonator body, respectively; and TCE I , E I , ρ I and V I represent the temperature coefficient of elasticity, Young's modulus, density and total volume of the second material in the array of spaced-apart trenches, respectively.