A bulk wave piezoelectric resonator operating at a predetermined frequency and comprising: a block of substrate (4; 64; 74), as holding means, with a plane face, having a first thickness e1 along a normal to said plane face, and made of a first material, and a resonant plate (6; 36; 66; 76), having first and second plane faces (8,10), which are positioned facing each other, the resonant plate having a length L, a width I and a second thickness e2, and being made of a second piezoelectric material, said second material being a piezoelectric material, first and second metal electrodes (12, 14; 42, 44; 54,56), covering at least partly the first face and the second face of the resonant plate (6; 36; 66; 76), respectively, and located at least partly facing each other, through the resonant plate (6; 36; 66; 76), the resonant plate (6; 36; 66; 76) being attached perpendicularly to the vicinity of the plane face of the block of substrate (4; 64; 74) so that the width of the resonant plate (6; 36; 66; 76) and the first thickness of the block of substrate (4; 64; 74) have a same direction, and the first material, the second material, the first thickness of the block of substrate (4; 64; 74), the length L, the width I, the second thickness e2 of the resonant plate (6; 36; 66; 76) being configured for trapping bulk waves at the operating frequency of the resonator and for producing a bulk wave piezoelectric resonator of the plane-plane type, i.e. bulk waves propagating in the direction of the thickness of the resonant plate, characterised in that the surfaces of the resonant plate cut by sawing are polished surfaces having a roughness of a few tens to a few RMS nanometers, and in that the piezoelectric resonator comprises an attachment element and/or an acoustic insulation element (68;78) at the operating frequency f, distinct from the block of substrate (64;74) and the resonant plate (66; 76), made of at least one third material distinct from the first and second materials, the attachment element and/or acoustic insulation element (68; 78) being comprised in a group made of a single adhesive layer and a Bragg mirror formed by a stack of layers with contrasted acoustic impedances. a block of substrate (4; 64; 74), as holding means, with a plane face, having a first thickness e1 along a normal to said plane face, and made of a first material, and a resonant plate (6; 36; 66; 76), having first and second plane faces (8,10), which are positioned facing each other, the resonant plate having a length L, a width I and a second thickness e2, and being made of a second piezoelectric material, said second material being a piezoelectric material, first and second metal electrodes (12, 14; 42, 44; 54,56), covering at least partly the first face and the second face of the resonant plate (6; 36; 66; 76), respectively, and located at least partly facing each other, through the resonant plate (6; 36; 66; 76), the resonant plate (6; 36; 66; 76) being attached perpendicularly to the vicinity of the plane face of the block of substrate (4; 64; 74) so that the width of the resonant plate (6; 36; 66; 76) and the first thickness of the block of substrate (4; 64; 74) have a same direction, and the first material, the second material, the first thickness of the block of substrate (4; 64; 74), the length L, the width I, the second thickness e2 of the resonant plate (6; 36; 66; 76) being configured for trapping bulk waves at the operating frequency of the resonator and for producing a bulk wave piezoelectric resonator of the plane-plane type, i.e. bulk waves propagating in the direction of the thickness of the resonant plate, characterised in that the surfaces of the resonant plate cut by sawing are polished surfaces having a roughness of a few tens to a few RMS nanometers, and in that the piezoelectric resonator comprises an attachment element and/or an acoustic insulation element (68;78) at the operating frequency f, distinct from the block of substrate (64;74) and the resonant plate (66; 76), made of at least one third material distinct from the first and second materials, the attachment element and/or acoustic insulation element (68; 78) being comprised in a group made of a single adhesive layer and a Bragg mirror formed by a stack of layers with contrasted acoustic impedances.