Method for forming semiconductor device

A method for forming a semiconductor device includes forming a dielectric layer conformally over a plurality of fins on a substrate, forming a first high-k layer conformally over the dielectric layer,and forming a flowable oxide over the first high-k layer. Forming the flowable oxide includes filling first trenches adjacent fins of the plurality of fins. The method further includes recessing theflow able oxide to form second trenches between adjacent fins of the plurality of fins, forming a second high-k layer over the first high-k layer and the flowable oxide, performing a planarization that exposes top surfaces of the plurality of fins, and recessing the dielectric layer to form a plurality of dummy fins that include remaining portions of the first and second high-k layers and the flowable oxide. 一种半导体装置的形成方法，包括在基底上的多个鳍片的上方顺应性的形成一介电层；在介电层的上方顺应性的形成第一高介电常数层；以及在第一高介电常数层的上方形成可流动的氧化物。形成可流动的氧化物包含填充多个鳍片的相邻鳍片之间的第一沟槽。此方法还包括使前述可流动的氧化物下凹，以在多个鳍片的相邻鳍片之间形成第二沟槽；在第一高介电常数层及可流动的氧化物的上方形成第二高介电常数层；进行平坦化工艺以暴露出鳍片顶面；以及下凹介电层以形成多个虚置