An integrated circuit chip including a plurality of parallel wells of alternated conductivity types formed in the upper portion of a semiconductor substrate of a first conductivity type, and a device of protection against attacks including: between the wells, trenches with insulated walls filled with a conductive material, said trenches extending from the upper surface of the wells to the substrate; and a circuit capable of detecting a modification of the stray capacitance formed between said conductive material and a region of the chip.