a physical quantity sensor for detecting a physical quantity includes : a first substrate having a first physical quantity detection element ; a second substrate having a second physical quantity detection element , wherein the second substrate contacts the first substrate ; and an accommodation space disposed between the first substrate and the second substrate . the first physical quantity detection element is disposed in the accommodation space . the first physical quantity detection element is protected with the first substrate and the second substrate since the first physical quantity detection element is sealed in the accommodation space .