他是如此的害怕以至于他不敢动一步.
这是so...that 句式的倒装,so + 表语提前 + be + 主语 + that 从句
如 So shallow is the river that we can walk across it.
So clever is the boy that everybody likes him.
但如果是形容词但不做表语,或副词,则部分倒装
如:So fast did he run that nobody could catch him.
So heavily did it rain that we had to delay the match.